Navigating the world of boating and sailing requires a good understanding of many nautical terms. From the anatomy of a boat to the mechanics of sailing, there are many terms that any boater or sailor needs to know.
Knowing some basic nautical terms is vital for safety, effective communication, and mastering the art of boating and sailing, whether you’re a seasoned sailor or a novice.
In this article, we’ve gathered 500+ nautical terms to cover general boating and sailing jargon. Enhance your knowledge and sail with confidence!
Without further ado, let’s explore the fascinating language of boating.
Nautical terms list
Aback– when the wind strikes the sails from the opposite side of the vessel than intended (lee side).
Abaft – toward the stern or rear of the boat.
Abaft the beam – a point on the boat’s side or stern that is behind a line perpendicular to the beam, which is the widest part of the boat.
Abeam – at right angles to the centerline of a boat.
Aboard – on or in a boat.
Abreast – side by side.
Adrift – a boat that is floating without any propulsion or anchor holding it in place.
Aft – toward the back of the ship (stern).
Aground – a boat that has run aground or is stuck on a reef or sandbar.
Ahead – forward of the ship, in forward direction.
Ahoy – a nautical greeting used to call or draw attention.
Aids to Navigation – navigational tools such as lighthouses, buoys, and beacons, that supplement natural landmarks, to help boats navigate safely.
AIS – Automatic Identification System.
Alee – side of the boat that is sheltered from the wind, opposite to windward.
Aloft – overhead, above the deck of the boat. .
Amidship – at or near the middle part of the boat.
Anchor – a heavy object used to grip to the ground underwater and keep a boat in place.
Anchorage – a suitable place in a body of water where boats can anchor or moor.
Apparent wind – The perceived wind speed and direction experienced the crew on a moving boat.
ARPA – Automatic Radar Plotting Aid.
Astern – behind or towards the rear of a boat. Opposite to ahead.
Athwartships – perpendicular to the centerline of a ship or boat.
Aweigh – the position of an anchor when it is being lifted from the seabed.
Azimuth – horizontal angle between a fixed reference point and the direction or bearing of an object. Typically measured in degrees and clockwise direction.
Back a sail – process of reversing the direction of a sail in order to slow down or stop a boat.
Backstay – a wire or rope that supports the mast from the stern of the boat and prevents its forward movement.
Backwinded – when the wind hits a sail on the opposite side to which it was intended to be set.
Baggywrinkle – protective covering that is placed on the rigging of a sailing vessel to prevent wear and tear from the sails.
Bail – to remove water from a boat using a bucket or other container.
Bailers – devices used for removing water from a boat.
Bale – a large bundle or package of goods or supplies that are tightly bound together for storage or transportation on a boat.
Ballast – a heavy material that is placed in the hull of a ship or boat to increase its stability and control its buoyancy.
Ballast keel – type of keel designed to provide ballast to a sailing vessel, typically a sailboat or yacht.
Bar – a shallow area of water that forms at the entrance or exit of a harbor or river.
Barber hauler – a line or wire attached to the jib or spinnaker sheet used to adjust its angle.
Batten – a thin, flat piece of wood or metal used to reinforce a sail.
Batten down – to secure hatches and other openings on a boat to prevent water from entering.
Beam – the widest part of a boat, usually in the middle.
Beam reach – a point of sail where the wind is blowing perpendicular to the side of the sailboat.
Bear away / Bear off – to steer the boat away from the wind.
Bearing – compass direction of an object relative to the boat’s position and expressed in degrees from true or magnetic north.
Beat – to sail upwind by tacking back and forth (zigzag) at an angle to the wind.
Belay – to secure a rope or line to a cleat or other fitting to prevent it from running out.
Below – lower deck or level of a boat.
Bend – to tie or fasten a rope or line to an object, such as a sail or anchor, using a knot or hitch.
Berth – (1) a place in a harbor where a boat can be docked or moored. (2) a bed or sleeping area on a boat.
Bight – bend or loop in a rope.
Bilge – the lowest part of a boat’s hull where water that enters the boat collects.
Binnacle – a case that holds a boat’s compass.
Bitter end – the end or final part of a line or chain.
Blanketing – a tactical sailing maneuver where one boat blocks the wind from reaching another boat to slowing it down.
Block – a pulley used to change the direction or mechanical advantage of a rope.
Bluewater sailing – to sail on the open ocean as opposed to coastal or lake sailing.
Boat – a craft or vessel designed to float on water and typically propelled by oars, sails, or an engine. Can be used for transportation, recreation, or commercial purposes.
Boat hook – device used for reaching or pulling objects in the water, or for pushing off from docks or other boats.
Boatswain – (pronounced “bosun”) a crew member responsible for the maintenance of the boat and its equipment.
Bobstay – supporting wire stay that runs from the bow of a boat to the end of the bowsprit, helping to hold it steady and secure.
Bollard – a short, thick post used for securing ropes or cables on a ship or dock.
Bolt Rope – a rope sewn onto the edge of a sail, to attach the sail to the rigging of the boat.
Boom – horizontal spar that extends from the mast of a sailboat and holds the foot of the sail.
Boom Crutch – a device used to hold the boom up and in place when the sail is not in use, usually while the boat is anchored or moored. The crutch is stowed when the boat is sailing.
Boom vang – a device on a sailboat that helps control the shape and tension of the mainsail by applying downward force to the boom. Helps to control the sail’s twist, and keep the boom from lifting.
Boot stripe – painted stripe on the hull of a boat that runs the length of the boat at or near the waterline.
Boot tope – a boot stripe at the boat’s designed waterline.
Bow – the front or forward section of the boat.
Bowline – (1) a docking line at the bow or forward part of the boat.(2) knot used to create a fixed loop at the end of a line that will not slip or come undone under load.
Bow thruster – a device used to maneuver a boat in tight spaces.
Bowsprit – a spar extending forward from a ship’s bow, primarily used to anchor the forestay for the jib or other headsails.
Breast line – a dock line going perpendicular from the centerline of the boat to the dock. Used to temporarily hold a boat close to the dock.
Bridge – the area of a ship from which it is navigated and controlled.
Bridle – line or wire attached to the boat at both ends and used to distribute the load.
Brightwork – varnished or polished surfaces such as wood or metal on a boat.
Broach – when a boat suddenly turns broadside to the wind and waves, causing it to heel over excessively and potentially leading to a loss of control.
Broad reach – point of sail where the wind is coming from behind the boat but not directly downwind.
Bulkhead – a dividing wall or partition separating different compartments within a boat.
Bullseye – a block with one or more holes through the center used for leading lines, halyards, or sheets.
Bulwark – vertical extension of the boat’s hull that increases the height of the sides and helps to prevent water from coming on board and to keep the crew in.
Bunk – narrow bed often built into the wall or arranged in tiers to maximize space.
Buoy – a floating device used as a navigational aid or to mark the location of hazards or obstructions.
Burdened vessel – a vessel that, according to navigational rules must give way to a “privileged vessel”. It is more commonly called a “give-way” vessel.
Cabin – an enclosed area on a boat used for living quarters or storage.
Cabin sole – the floor or deck of the cabin on a boat.
Cable – (1) Heavy chain or rope attached to an anchor. (2) A unit of length equal to 120 fathoms or 720 feet (219 meters) in US customary units (USCS).
Can – a type of navigational buoy.
Canvas – material used for sails in the early days. Still used for boat covers, dodgers, biminis, and other accessories.
Capsize – to turn over or flip a boat.
Capstan – a machine used to raise heavy objects such as anchors.
Cargo – goods or materials transported by ship or other means of transport.
Cast off – to untie a boat from a mooring or dock, or to release a line from a cleat or bollard.
Catamaran – a boat with two parallel hulls.
Catboat – sailboat with a single sail mounted on a mast set well forward in the bow of the boat.
Celestial navigation – method of navigating a boat by using the positions of celestial bodies such as stars, the moon, and planets.
Centerboard – a board lowered through a slot in the centerline or keel to help reduce sideways drift. Also spelled centreboard.
Centerline – line at the center of a sailboat, from the bow (front) to the stern (rear), that divides the boat into port and starboard halves.
Chafe – damage to a line, or cable caused by rubbing against a rough surface or another object.
Chafe gear/ Chafing gear – gear used to prevent chafe. Chafe gear materials commonly include rubber, canvas, and leather.
Chain plates – metal plates that are part of the sailboat rigging system, and are used to attach shrouds and stays to the deck.
Chart – a map used for navigation.
Chart datum – level surface provided on a chart and used by boaters to determine water depth at any given point and to ensure safe passage.
Chine – intersection between the bottom and sides of a boat, that creates an angle or ridge along the hull. Not found in round bottom boats.
Chock – a fitting attached to the deck and used to guide anchor, mooring or dock lines.
Clear the decks – to remove or tidy up everything from a boat’s decks to prepare for action or to clean the ship.
Cleat – a fitting on a boat’s deck to which a rope or chain can be tied.
Clew – the lower aft corner of a triangular sail or the lower corners of a four-sided sail.
Close hauled – a point of sail where the boat is sailing as close to the wind as possible.
Close reach – point of sail where the wind is coming over the side of the boat at an angle between a beam reach and a close hauled.
Clove hitch – a type of knot used to attach a line to a post, pole, or another line.
Coaming – raised edge or border around an opening or a raised area on a boat to prevent water from entering the cockpit, hatch, or other openings.
Cockpit – the area of a boat or ship where the steering and navigation equipment is located.
Coil – to arrange a line in a series of circular loops, ready for stowing.
Comms – short for “communications”, referring to communication equipment and systems on a ship.
Companionway – a stairway or ladder leading from one deck to another.
Compass – a navigational instrument used to determine direction relative to the Earth’s magnetic poles.
Compound sheer – curvature of a boat’s deck from the bow to the stern, where the height of the deck changes both horizontally and vertically. .
Container ship – a type of ship designed to transport standardized shipping containers.
Course – the intended direction of a boat’s movement.
Coxswain – the person who steers and directs a small boat.
CQD – a distress signal used in radio communication before the adoption of SOS. A combination of two signals: “CQ” (“sécu“, from the French word sécurité) which means “alert message to all stations”, and “D” to indicate “distress”. See meaning of CQD.
Crane – a machine used for lifting and moving heavy objects on a boat.
Crew – the people who operate a boat.
Cringle – small eye or grommet in a sail used to attach lines or fittings.
Cuddy – small shelter on a boat used for storage or for the crew to take refuge from the weather.
Cunningham – a control line that is used to adjust the tension of the luff (forward edge) of a sail.
Current – the flow of water in a particular direction, often caused by tides or winds.
Cutter rig – a type of sailboat rigging that features two or more head sails, or foresails, mounted on the forestay.
D signal – a signal used in maritime communication to indicate “keep clear, I am maneuvering with difficulty.” It is represented by a yellow and blue square flag (Delta flag).
Daggerboard – similar to a centerboard, it slides up and down in a slot in the hull. Common on catamarans, trimarans, and some small monohull sailing boats.
Davit – a crane-like device used for lowering or raising small boats on a ship.
Dead ahead – Directly in front of the boat and its centerline.
Dead astern – Directly behind the boat or straight aft.
Dead reckoning (DR)/ Deduced reckoning – estimated position based on course, speed, and time from a known past position.
Dead run – when the wind is directly behind a sailboat. The boat is running directly downwind.
Deadhead – a floating log or piece of timber that poses a hazard to navigation.
Deadlight – a type of weather cover designed to fit into a larger opening in a boat’s hull or deck and used to close off an opening in bad weather.
Deck – the horizontal surface of a boat’s hull above the waterline.
Deck plate – a metal or plastic plate that covers an opening in the deck of a boat, providing access to equipment or storage spaces such as the bilge or fuel tank.
Depth sounder – a device used to measure the depth of water.
Deviation – difference between the true north and magnetic north which affects the accuracy of the compass. Is caused by a vessel’s own magnetic field or metallic objects.
Dinghy – small boat often used as tenders to larger boats, to ferry people and supplies to and from shore.
Displacement – (1) the weight of the water displaced by the boat when afloat. (2) the weight of the boat itself, including all the equipment, fuel, and supplies on board.
Displacement hull – a hull design that displaces a volume of water equal to the boat’s weight for improved buoyancy.
Dock – a structure built along the shore or waterfront for boats to moor, tie up, or load and unload passengers or cargo.
Dodger – cover that extends above the cockpit of a boat to provide shelter from wind, spray, and rain.
Double ender – a type of boat or ship that has a pointed bow and stern, which are similar in shape and size, allowing for better stability and maneuverability.
Downhaul – a line used to apply downward tension or pull on a sail or other piece of equipment.
Downwind – when the wind is blowing from behind a vessel or in the same direction the boat is traveling. Sailing away from the wind.
Draft – the depth of a boat’s hull below the waterline.
Drift – distance and direction a vessel is carried off course due to external forces such as wind, waves, or current.
Drogue – sea anchor device that is attached to the boat by a line and deployed overboard to create drag and slow down drift.
Drop keel – a retractable keel that can be lowered and raised as needed.
Dry dock – a structure used for repairing, building, and maintaining boats out of the water.
DSC – Digital Selective Calling, a method of communication used in maritime radio systems.
Ease – to slacken or loosen.
Ebb – the flow of tidewater away from land, usually occurs between high and low tide.
EP – Estimated Position.
EPIRB – Emergency position indicating radio beacon, a device used to alert search and rescue services in case of an emergency.
ETA – Estimated Time of Arrival.
ETD – Estimated Time of Departure.
Fairlead – a fitting on a boat’s deck used to guide ropes or cables.
Fairway – a navigable channel or area of water.
Fall off – to steer a vessel away from the wind. Also known as Head Down.
Fathom – a unit of measurement equal to 6 feet (1.83m), used to measure water depth.
Fender – a cushioning device, placed between boats, or between a boat and a pier, to prevent damage.
Ferry – a boat or ship used to transport passengers and vehicles across a body of water.
Fiddle – a raised guard around the edge of a table, counter, or other flat surfaces to prevent objects from falling off.
Figure Eight Knot – a type of stopper knot, that looks like the number eight, and is used to prevent the end of a rope from passing through a retaining device such as a ring, grommet, or block.
Figurehead – a carved ornament mounted on the bow of a boat.
Fix – the vessel position determined by taking bearings or sightings on three or more objects or landmarks.
Flare – (1) a device used to signal for help or to mark the location of a person or object in the water. (2) the outward curve of a boat.
Fleet – a group of ships.
Float – a buoyant object used for marking channels or hazards in the water.
Flood – the incoming or rising tide. Opposite to ebb.
Flotsam – debris or wreckage from a ship that is floating on the surface of the water.
Fluke – the part of an anchor that digs into the seabed to hold the vessel in place.
Foghorn – a loud horn used to signal in foggy conditions.
Following sea – wave pattern approaching a vessel from astern, following the vessel’s direction of travel.
Force 8 – gale level winds with average speeds of 34 to 40 knots (39 to 46 mph) according to the Beaufort Wind Scale. Level 12 is a hurricane.
Fore – towards the front or bow of a ship.
Forecastle – Sometimes abbreviated fo’c’sle, the forward-most part of the ship, often used as the crew’s living quarters.
Foredeck – the boat’s deck at the bow or front of the vessel.
Foremast – the mast located nearest to the bow (front) on a boat with more than one mast. Usually the second tallest mast.
Forepeak – small compartment at the forward end of a ship, below deck, and used for storage of equipment, sails, or anchors.
Foresail – sail located forward of the mast on a sailing vessel.
Forestay – a stay that supports the mast from the front of the boat.
Foretriangle – the triangular area of sail between the forestay, mast, and deck of a sailing vessel.
Forward – towards the front or bow of a boat.
Fouled – Fouled- entangled or obstructed.
Fractional rig – Fractional rig- sailing rig in which the forestay does not run to the top of the mast but instead attaches at a point below the top, or “fractional” point.
Freeboard – the vertical distance between the waterline and the main deck of a boat.
Furl – to roll up and secure a sail.
Gaff – a spar positioned diagonally across the mast and used to support and control the sail.
Galley – the ship’s kitchen or cooking area.
Gangway – a movable ramp or platform used for boarding or disembarking a boat.
Gasket – a rope used to secure a sail to a spar or mast. Term mainly used in square-rigged ships.
Gear – various pieces of equipment and supplies used to operate and maintain a boat, including sails, lines, winches, anchors, electronics, safety gear, etc.
Genoa – a type of headsail that is larger than the jib and overlaps the mainsail. It is said the sail originated in Genoa Italy, hence its name.
Gimbals – a device used to keep a compass or other instrument level and stable.
Give – a vessel that requires taking action and keeping clear of the Stand-on vessel.
GMDSS – Global Maritime Distress and Safety System.
GMT – Greenwich Meridian Time. Became Coordinated Universal Time (UTC) in 1972.
GNSS – Global Navigation Satellite System.
Go about – to turn the boat through the wind during the tack.
Going to weather – sailing against wind and seas.
Gooseneck – fitting that attaches the boom of a sailboat to the mast. Designed to allow the boom to pivot up and down and side to side.
GPS – Global Positioning System, a satellite-based navigation system used for determining location and navigation path.
Grab rails – cabin fittings for hand-holding and personal safety when moving around the boat.
Great Circles – method of defining the shortest distance between two points on the globe’s surface.
Grog – a mixture of rum and water served to sailors in the 18th century.
Ground tackle – equipment used to anchor a boat. Includes the anchor, anchor chain or rope, and any other equipment required for anchorage.
Grounding – when a boat runs aground on a shallow area or rocks.
Guard rail – also known as a lifeline, is a safety railing system that runs around the perimeter of a boat, to prevent crew and passengers from falling overboard.
Gunwale – the upper edge of a boat’s side.
Guy – a steadying line used to control the end of a spar.
Gybe – another term for jibe.
Half – a flag flown at a lowered position as a sign of mourning.
Halyard – a rope or line used for hoisting or lowering a sail.
Hanks – metal fittings or hooks used to attach a sail to a stay of a sailboat.
Hard alee – a command given on a sailing vessel to turn the helm and have the bow of the boat through the wind as quickly as possible.
Hard Chine – hard or abrupt intersection between the bottom and sides of a boat, that creates an angle or ridge along the hull. Not found in round bottom boats.
Hard over – to turn the steering wheel as fast as possible.
HAT – Highest Astronomical Tide.
Hatch – an opening in a boat’s deck used for access or ventilation.
Hawser – a large rope used for towing or mooring a ship.
Head – (1) the toilet or bathroom on a boat (2) the upper corner or end of a triangular sail.
Head Down – to steer a vessel away from the wind. Also known as Fall Off.
Head to Wind – when the bow of the boat points directly into the wind.
Header – when wind direction changes, causing the boat to head down.
Headfoil – streamlined rod surrounding the forestay, and used to furl and unfurl the headsail.
Heading – the direction in which a boat bow is pointed or aimed. Usually expressed as an angle in degrees relative to the north or another reference.
Headsail – sail located forward of the mast on a sailing vessel. See Foresail.
Headstay – a stay that supports the mast from the front of the boat. See Forestay.
Headway – forward motion or progress made by a vessel through the water. opposite to sternway.
Heave to – to stop a boat’s forward progress.
Heel – the lean of the boat to one side and caused by the winds force on the sails.
Helm – the steering apparatus of a boat, including the wheel or tiller.
Helmsman – crew member at the helm and responsible for steering the boat.
Helmsperson – person who steers the boat. See Helmsmans.
Hike – to lean out over the side of the boat to balance it.
Hike out – the practice of leaning over the windward side of a sailboat in order to keep it balanced and prevent it from tipping over.
Hiking stick – a device used to control the tiller from a certain distance.
Hitch – a knot used to attach a rope or line to an object, such as a post, ring, or hook.
Hoist – to raise something, usually a sail, up a mast or spar using halyards or other lines.
Hold – the interior space of a ship or vessel used for storing cargo or goods.
Hook – slang for anchor.
Hove to – see heave to.
Hull – the main body or frame of a boat.
Hull speed – the maximum speed at which a keelboat can travel through the water.
Icebreaker – a type of ship designed to navigate through ice-covered waters.
IMO – International Maritime Organisation.
In irons – when a sailboat heads directly into the wind, becomes stuck or stalled, and is unable to move forward or steer effectively.
Inboard – inside the hull of a boat, as opposed to outside or outboard.
IOR – International Offshore Rating.
IRPCS – International Regulations for Preventing Collisions at Sea.
Isobars – lines that connect points of equal atmospheric pressure on a weather map.
ITU – International Telecommunication Union.
Jack line – a length of webbing or wire that is secured to a boat’s deck, running fore and aft, that is used to attach a safety harness and tether to the boat.
Jackstay – a line or wire that runs between two points on a vessel to support or guide a load between those points.
Jacobs Ladder – a rope ladder that is used to climb aboard a ship or to climb up to the crow’s nest of a mast.
Jetsam – goods or materials intentionally thrown overboard from a ship in distress to lighten the ship’s load. Different from flotsam, where items are accidentally lost and float at sea.
Jetty – a long structure that extends from the shore into a river or ocean. Used as a platform for fishing or for docking boats. Typically made of concrete, stone, or other materials.
Jib – a triangular sail at the front of a boat.
Jibe – to turn a sailboat so the wind hits the sail from the opposite side by turning the boat’s stern through the wind. Also Gybe.
Jiffy reefing – a technique used to quickly reduce the sail area of a sail in high winds.
Jury – a temporary arrangement or makeshift repair used to replace damaged or lost gear.
Kedge – small, secondary anchor of a boat.
Keel – the centerline structure running along the bottom of a boat’s hull.
Keelson – a longitudinal beam or structure that runs along the bottom of a boat hull, parallel to the keel, typically found in larger vessels.
Ketch – a two-masted sailboat, with the main mast located forward and the smaller mizzen mast aft.
Kicking strap – also known as a boom vang or simply a vang, is a line or mechanical device used to control the boom on a sailboat.
Knot – a unit of speed equal to one nautical mile per hour (1 knot = 1.15 miles per hour = 1.85 kilometers per hour).
Landfall – the first sighting or arrival at land after a voyage at sea.
Lanyard – a line used for securing or attaching equipment on a boat.
LAT – Lowest Astronomical Tide.
Latitude – a measure in degrees of a boat’s position north or south of the equator.
Launch – (1) to put a boat into the water from a dry dock or trailer (2) a small, open motorboat used for short trips to and from shore or ship.
Lazarette – small storage compartment on a boat, typically located aft and below the cockpit or deck.
Lazy jack – lines used to help control the mainsail of a sailboat when it is being lowered.
Lead – term used to indicate the direction in which a line runs.
Lee – the sheltered side of a boat, away from the wind.
Lee cloths – pieces of fabric or netting used to create a barrier along the side of a berth (sleeping area) to prevent the user to slide out due to boat movement.
Lee helm – condition where the boat tends to steer away from the wind.
Lee shore – a coast or shoreline located to the lee (downwind) of a boat. It is generally recommended to keep a safe distance from lee shores when navigating in windy or rough conditions.
Leech – the rear edge of a sail, typically the edge of the sail that is not attached to a mast, spar, or another rigging.
Leech Line – a line used to tighten the leech.
Leeward – the direction away from the wind. Opposite to Winward.
Leeway – the sideways drift of a boat caused by wind force or currents.
Life Jacket – A buoyancy aid that helps a person float and stay afloat in the water, reducing the risk of drowning. Also known as a Personal Flotation Device (PFD).
Lifeline – a line or cable used to prevent crew members from falling overboard.
Lifesaving equipment – devices used to save lives in case of an emergency, such as lifeboats, life rafts, and life jackets.
Light – a navigational aid used to indicate the location of hazards or to guide ships into port.
Lighthouse – a tower or structure with a bright light used to guide ships at sea.
Line – a rope or cable used on a boat for various purposes, such as securing cargo or tying up to a dock.
List – the leaning or tilting of a boat to one side due to uneven weight distribution.
Log – (1) device used to measure a boat’s speed and distance traveled (2) a record of the details of a voyage. See logbook.
Logbook – a record of a boat’s activities, including its course, speed, and events.
Longitude – a measure, in degrees, of a boat’s position east or west of the Prime Meridian.
Lubber’s line – reference line or mark on a boat’s compass that helps the user determine the boat’s heading or direction of travel.
Luff – the edge of a sail closest to the wind.
Mainsail (Main) – the largest and most important sail on a sailboat, is typically attached to the mast and boom.
Mainsheet – the line that controls the position and tension of the mainsail. It is typically attached to the aft end of the boom and runs aft to the cockpit.
Manning – the act of providing personnel to operate a ship.
Mariner – a person who navigates or operates a ship.
Marlinspike – a tool used for working with ropes and knots. Has a pointed end for separating strands, and a flattened end for splicing.
Mast – a tall vertical pole that supports the sails.
Mast step – fitting or structure on a sailboat that supports the bottom of the mast and attaches it to the hull.
Masthead rig – type of rig in which the forestay attaches to the mast at the very top of it, or masthead.
Mayday – distress signal used in radio communications to signal a life-threatening emergency on board.
MCA – Maritime and Coastguard Agency (UK).
Measured mile – one nautical mile, typically marked with buoys or other navigational aids, used to measure the speed and performance of a boat.
Meridian – a line of longitude that runs north-south and passes through both the North and South Poles.
MHWN – Mean High Water Neaps.
MHWS – Mean High Water Springs.
Midship – Approximately the central section of a boat, typically the widest part of the hull.
Mizzen – the aft-most mast on a ship.
MLWN – Mean Low Water Neaps.
MLWS – Mean Low Water Springs.
MMSI – Maritime Mobile Service Identity.
Mooring – the act of securing a boat to a dock or buoy.
Motor – when sails and motor are used simultaneously on a sailboat.
Nautical mile – a unit of distance used in navigation, equal to one minute of latitude. A nautical mile is slightly more than a standard mile. 1 nautical mile = 1.15 miles = 1.85 kilometers.
Navigation – the process of planning and directing the course of a boat.
Navigator – a person who plans and directs the course of a boat.
Nun – a navigation aid used to indicate the edge of a navigable channel or the location of a hazard.
Oar – a long, narrow paddle used to row a boat.
Offing – refers to the open sea, particularly a safe distance from the shore.
Old salt – experienced sailor who has spent a significant portion of their life at sea.
Onboard – on or in the ship.
Outboard – (1) away from the centerline of a boat (2) a detachable engine mounted on the stern of a boat.
Outhaul – a line that controls the tension and position of the sail along the boom.
Overall length (OAL) – the maximum length of a vessel, measured from the outermost point at the bow to the outermost point at the stern, including any protrusions or extensions.
Overboard – over the side of the ship.
P Flag – also called Blue Peter flag, is a nautical signal flag that indicates a ship is preparing to leave port. It is a blue flag with a white square in the center.
Paddle – a flat blade used for propelling a small boat through the water.
Painter – a rope or cable used to secure or tow a small boat to a larger ship or dock.
Pan Pan – radio call to request assistance from other vessels or authorities. Unlike Mayday, Pan-pan is used when there is no immediate danger to life or the vessel’s safety.
Pay out – to let out a rope or cable gradually. Opposite to paying out is “taking in” or “reeling in”.
Pedestal – column or base used to elevate and secure equipment, such as the steering wheel and controls, for easy access and stability.
Pennant – long, narrow, triangular flag that is typically used on boats and ships for signaling or identification purposes.
PFD – personal flotation device, also known as a life jacket.
Pier – raised structure that extends from the shore over the water and is used for docking boats, as well as for recreational activities.
Piling – a vertical support used to anchor a dock or pier.
Pilot – a person who navigates a ship through difficult or unfamiliar waters.
Pitch – the angle of a ship’s hull relative to the horizontal plane.
Planing – when a boat rises up and glides over the surface of the water, rather than displacing water as a traditional boat would.
Point of sail – the direction that a sailing vessel is traveling relative to the wind, e.g. beam reach, broad reach, upwind, downwind, etc.
Polaris – a star located in the constellation Ursa Minor, commonly known as the North Star or Pole Star. Used for centuries as a navigational aid.
Port – the left side of a boat when facing forward.
Port tack – sailing with the wind coming from the port side of the boat, and the sail is set to the starboard side of the boat.
Preventer – a line used to prevent the boom from accidentally jibing (moving suddenly and dangerously from one side to the other).
Privileged vessel – vessel that has the right of way over other vessels in certain situations as defined by navigation rules.
Proa – a traditional outrigger canoe with a single sail and a long, narrow hull.
Propeller – a device used to propel a boat through the water.
Pulpit – safety railing located at the bow of a boat that helps prevent people from falling overboard.
Q flag – a yellow flag that is flown by boat to indicate that it is healthy and to request free pratique (permission to enter a port or receive officials from shore).
Quarter – the side of a ship between the stern and amidships.
Quay – pronounced as “key” or “kee.” Is a wharf used for loading and unloading cargo or passengers from ships.
Radar – a device that uses radio waves to detect the presence and location of objects, used for navigation and collision avoidance.
Ratchet – a mechanism that allows a rope to be tightened in one direction only.
Reach – point of sail where the wind is coming from the side of the boat, at an angle between a close-hauled course (where the boat is sailing as close to the wind as possible) and a run (where the wind is coming directly from behind the boat). The three types of reach are close reach, beam reach, and broad reach, depending on the angle of the wind relative to the boat.
Ready about – to signal to the crew that the boat is about to tack, or turn into the wind.
Reef – to reduce the size of a sail by folding or rolling a portion of it.
Reeling in – to retrieve a fishing line or reel.
Rhumb line – a line that crosses all meridians of longitude at the same angle. Also called a loxodrome.
Rigging – the system of ropes, cables, and other devices used to support and control the sails of a boat.
Right of way – the privilege of a vessel to maintain its course over others based on established navigational rules. it is determined by the vessel type, position, course, speed, and other factors.
Roach – the curved portion of the sail that extends beyond a straight line drawn between the head and clew.
Rocker – upward curvature of a boat’s keel to the bow and stern.
Rode – the line or chain attached to the anchor and used to hold the boat in place while at anchor.
Roller reefing – to shorten the sail area by wrapping a sail around a boom or forestay.
Rope – cordage or line used aboard a vessel, including halyards, sheets, dock lines, and anchor lines. In nautical terminology, Line is frequently used instead of rope.
Rudder – a flat plate or blade attached to the stern of a boat and used to steer it.
Run aground – to ground a boat on a shallow area or rocks.
Run/running – to sail with the wind aft or directly behind the boat, which is the most downwind point of sail.
Running lights – lights required to be displayed on a boat underway between sunset and sunrise. Consist of red and green sidelights and a white stern light.
Running rigging – the lines such as sheets or halyards used to adjust the position of the sails.
Sail – a piece of fabric attached to a mast or spar and used to capture the wind to propel a boat.
Sail trim – the adjustments made to the sails on a sailboat to optimize their performance in different wind and sea conditions.
Sampan – a flat-bottomed boat typically used in China and Southeast Asia for transportation and fishing.
Samson post – a vertical post or bitt located on the deck or hull of a ship used for securing mooring lines or tow lines.
SAR – Search and Rescue.
SART – Search and Rescue Transponder.
Sat Nav – short for “satellite navigation” refers to the use of GPS to determine a boat’s position and navigate from one location to another.
Schooner – a sailing ship with two or more masts and fore-and-aft sails on the mainmast.
Scope – the ratio between the length of an anchor rode and the water depth. A higher scope, such as 7:1 or 10:1, means that more rode is paid out and the anchor is more securely set in the bottom, providing greater holding power for the boat.
Scull – a method of propulsion in a small boat where a single oar is moved back and forth behind the boat, with the oar pivoting at the stern rather than the side of the boat.
Scupper – a hole or channel in a boat’s deck that allows water to drain off.
Scuttle – to intentionally sink a boat by creating holes in the hull or opening its seacocks to let water in. Also refers to a small hatch or opening in a ship’s deck or hull that is used for ventilation, drainage, or access to equipment.
Scuttlebutt – a drinking fountain on a boat, or gossip among sailors.
Sea anchor – a device used to slow down or stabilize a boat in heavy seas.
Sea chest – a compartment in the ship’s hull for pumping seawater.
Sea Cock – a valve fitted to a boat’s hull which allows water to enter or exit through a hose or pipe. Used for draining water from the bilge or for providing water to the engine or other onboard systems.
Sea level – the level of the ocean’s surface used as a reference point for measuring elevation.
Sea room – a safe distance or area available for a boat to maneuver and navigate safely in open waters without colliding with other vessels, obstacles or running aground.
Seafarer – a person who travels by sea, especially for work or adventure.
Seamanship – skills, knowledge, and practices for operating a boat, as well as maintaining and caring for it.
Seaworthy – a boat’s capability to withstand harsh conditions and challenges of the sea.
Sécurité – term (french) used in marine radio communication to indicate a message that is about to be transmitted concerning the safety of navigation or important meteorological warnings.
Seelonce – term (French) used in marine radio communication to indicate that a distress call is being made and that all other radio traffic should cease.
Self – a feature in boats where any water that enters the cockpit is automatically drained or pumped out.
Set – (1) the trim of a sail (2) the direction in which a vessel is moving in relation to its intended course or direction (3) dropping an anchor and allowing it to settle.
Sextant – a navigational instrument used to determine a boat’s position by measuring the angles between the horizon and celestial objects such as the sun and stars.
Shackle – metal fastener with a removable pin or bolt used to connect two parts of a chain or rigging together or to attach a line or cable to an object.
Sheave – grooved wheel or roller of a block pulley used to guide and redirect lines.
Sheet – a line used to adjust the position of a sail.
Ship – a large seagoing vessel.
Ship’s bell – a bell used to mark time aboard a ship.
Shipshape – in good order and condition.
Shipwreck – the remains of a sunken ship.
Shore – the land bordering a body of water, typically where it meets the water.
Shroud – a rope or cable used to support the mast of a boat.
Skeg – a structural extension of the keel that runs aft beneath the boat’s hull.
Skipper – the captain or person in charge of a ship or boat.
Slack – to loose or not taut lines or cables. Lack of tension or looseness in a sail or other piece of equipment.
Sloop – a sailing vessel that has a single mast with one mainsail and a headsail.
Snubber – a device used to relieve tension on a boat’s anchor chain, prevent the chain from chafing against the boat’s bow, and reduce shock loads on the anchor and chain.
SOG – Speed Over the Ground.
SOLAS – Safety of Life at Sea. An international treaty established in 1914 that sets minimum safety standards for ships.
Sole – the floor or bottom surface of a boat’s cabin or cockpit.
Sonar – a device that uses sound waves to detect the presence and location of underwater objects, used for navigation and detecting hazards.
SOS – Morse code distress signal used as an international standard for emergency situations. Listen to an SOS signal.
Soundings – measurements of the depth of water in a particular area.
Spar – a long, slender pole used to support sails on a boat.
Speed log – a device used to measure a boat’s speed through the water.
Spinnaker – a large sail used for downwind sailing.
Splice – join two ropes to form a permanent loop in a single rope. Involves weaving the strands of the rope together to create a strong, permanent bond.
Spreaders – horizontal struts that are attached to a sailing boat’s mast to keep the mast from bending and to help control the shape of the sails.
Spring line – a line used to control the position of a boat while it is docked.
Squall – a sudden, sharp increase in wind speed, regularly accompanied by rain, thunder, and lightning.
Square knot – also known as a reef knot, is a basic knot used to join two ropes of equal size.
Stall – when the sail loses its ability to generate lift or control due to a lack of airflow.
Stanchion – vertical pole or post, made of metal or plastic, used to support a railing or guardrail.
Stand – a vessel that has the right-of-way and requires keeping her course and speed.
Standing part – the part of a line that is not actively used to perform a task, such as tying a knot or securing a line to a cleat.Opposite to the working end.
Standing Rigging – fixed lines or wires on a sailboat that support the mast and keep it in place. This includes the forestay, backstay, and shrouds. Different from the running rigging, which is used to control the sails and is adjusted frequently.
Starboard – the right side of a boat when facing forward.
Starboard tack – sailing with the wind coming from the starboard side of the boat, and the sail is set to the port side of the boat.
Stay – a line or wire that supports a mast from the bow (forestay), stern (backstay), or either side (sidestays).
Staysail – a type of sail that is set on a stay instead of a mast.
Steerage way – when a boat moving forward has enough water flowing over its rudder(s) to enable it to be steered effectively.
Stem – the forward-most part of a boat’s bow that curves upward to provide a shape for the hull to cut through the water efficiently.
Stern – the rear or aft part of a boat.
Stern line – a line used to secure the stern of a vessel to a dock, pier, or other mooring point.
Sternpost – the vertical post at the back of the ship’s hull.
Sternway – the reverse or backward motion of a boat.
Stores – the supplies or provisions needed for a vessel’s operation during a voyage.
Stow – to pack or store cargo or equipment on a ship.
Strake – a continuous line of planking or plating along the hull of a boat.
Sump pump – a device used to remove water that has accumulated in a pit or shower basin.
Swell – a long, rolling wave caused by wind or distant storms.
Tabernacle – a hinged support structure that enables a mast to be lowered and raised easily. Is a useful feature for sailboats that need to pass under low bridges or power lines.
Tack – (1) the lower forward corner of the sail. (2) To turn a sailboat’s bow through the wind so that the wind catches the opposite side of the sail. (3) noun used to indicate the direction the sailboat is sailing with respect to the wind e.g. port tack or starboard tack.
Tackle – a system of ropes and pulleys used to hoist or move heavy objects on a boat.
Taffrail – the rail or railing around the stern of a vessel, and is primarily used for safety.
Taking in – furling or reefing a sail to reduce its area.
Tang – metal fitting used to attach standing rigging, such as shrouds and stays, to a mast or spar.
Telltales – thin strips of cloth or yarn that are attached to a sail, used to indicate airflow and sail trim.
Tender – small boat used to ferry people and supplies to and from shore. Also called dinghy .
Thwart – a crosswise seat in a boat.
Tidal range – the difference in water level between high tide and low tide in a particular area.
Tide – the periodic rise and fall of water level caused by the gravitational pull of the moon and sun.
Tiller – a handle or lever used to steer a boat.
Toe rail – a narrow strip of wood, metal, or fiberglass molding along the edge of a sailboat’s deck near the hull, mainly used to secure a foothold for crew moving around the deck.
Tonnage – the total weight or volume of cargo that a vessel can carry, and usually expressed in either gross tonnage (GT) or net tonnage (NT).
Topmast – a mast situated above the lower mast on a ship.
Topsail – a sail set on the top of a ship’s mast.
Topside – the upper part of a boat’s hull.
Track – a device or structure that allows a sail or other object to move along a fixed path.
Trampoline – netting that is stretched between the hulls of a catamaran or trimaran, providing a stable and comfortable surface for passengers to relax on.
Transom – the flat, vertical surface at the stern of a boat.
Trapeze – wire and equipment used on a sailing boat to allow crew members to hang out outboard to counterbalance the force of the wind on the sails.
Traveler – device that allows the mainsail to be moved horizontally along the boat.
Trim – to adjust the sails or ballast to maintain a boat’s stability and speed.
Trimaran – a type of multihull boat consisting of a main hull and two smaller outrigger hulls called amas, attached to the main hull with lateral struts.
True north – the direction of the North Pole.
True wind – actual speed and direction of the wind experienced when there is no other movement or influence.
Tuning – process of adjusting the rigging and sails of a sailboat to optimize performance and balance in different wind and sea conditions.
Turnbuckle – device used for adjusting the tension or length of lines, cables, tie rods, and other tensioning systems.
Turning mark – buoy or other fixed object used in sailing or boat racing to mark a course change.
Turtling – when a boat capsizes, with the mast pointing down towards the sea bottom.
Underway – a boat that is in motion.
Unmoor – to release a boat from its moorings.
Uphaul – a line used to hoist a sail, flag, or spar up to the masthead.
Upwind – the direction that is facing or heading towards the wind. See beat.
V berth – bed in “V shape” typically found in the forward cabin of a boat. .
V bottom – also known as a V-hull, is a type of boat hull design that features a V-shaped hull that slices through the water.
Vang – see boom vang and kicking strap.
Veer – (1) change of wind direction clockwise. (2) To pay out or let out more line or chain, allowing a vessel to move farther away from its anchor point.
Vessel – a general term for any type of watercraft.
VHF – Very High Frequency.
Victuals – food or other provisions.
Vittles – see victuals.
VMG (Velocity Made Good) – speed at which a sailboat can make progress towards its destination while accounting for the effects of wind direction and currents.
Wake – the trail of disturbed water left behind by a moving ship.
Warship – a ship equipped for combat.
Watch – period of time during which one or more crew members are responsible for operating a vessel.
Waterline – the line where a boat’s hull meets the water.
Wavelength – distance between two consecutive points of the same phase on a radio wave.
Way – the forward movement of a boat through the water.
Waypoint – a predetermined location on a boat’s course.
Weather deck – the uppermost deck exposed to the elements on a ship.
Weather helm – the tendency of a boat to turn into the wind when the helm is released.
Wheel – a circular steering device used to steer a boat.
Whisker pole – also known as a spinnaker pole, is a horizontal spar used for jibing and holding out the clew of a jib or spinnaker.
Winch – mechanical device used to wind in or let out a cable or rope under tension.
Wind rose – a graphic tool used to visualize the distribution of wind directions and speeds at a particular location over a specific period of time.
Windage – the effect of wind on a boat or parts of it, that can cause it to drift or experience a lateral force.
Windlass – a mechanical device used on a boat to help with the raising and lowering of heavy equipment such as an anchor or sails.
Windward – the direction from which the wind is blowing. Opposite to Leeward.
Working end – the part of a line that is actively used to perform a task, such as tying a knot or securing a line to a cleat. Opposite to the standing part.
XTE (Cross Track Error) – perpendicular distance between a vessel’s actual position and its intended track.
Yacht – a pleasure boat used for cruising or racing.
Yard – a horizontal spar attached to a mast used to support a sail.
Yaw – movement or rotation of a vessel around its vertical axis that occurs when the boat is underway.
Yawl – a type of sailboat with two masts, with the smaller mizzen mast located aft the rudder post.
Zincs – type of sacrificial anodes used to protect boats and other underwater structures from corrosion.