Boating Terminology Glossary With 150 Essential Terms

Cruising sloop sailing on Lake Constance. Photo: Matti Blume, CC BY-SA 4.0, source

On this page

The hull and its structure
Directions and positions aboard
Deck, hardware and fittings
Lines, knots and rope handling
Sails, rig and sail handling
Engines, drives and hull behavior
Navigation, charts and electronics
Rules of the road, radio calls and seamanship
Docking, mooring and anchoring
Weather, tides and sea state
Ownership, buying and accommodation
FAQ

The hull and its structure

Boating terminology can sound like an old club's private language, but almost every word earns its place. On a moving boat, in wind, with engines running, short and unambiguous words prevent accidents. Shouting 'line on the starboard aft cleat' tells one person exactly what to do, while 'that rope on the right at the back' depends on which way they are facing.

The glossary groups 150 terms by theme, starting with the hull and working outward to deck gear, lines, sails, propulsion, navigation, the rules of the road, anchoring, weather and ownership. These first words are the ones a surveyor, broker or builder uses when describing what the boat is made of and how it meets the water.

Term	Meaning
Hull	The watertight body of the boat, not counting deck, superstructure or rigging.
Bow	The front end of the boat.
Stern	The back end of the boat.
Transom	The flat or slightly curved surface across the stern, where outboards and swim platforms mount.
Keel	The backbone along the bottom of the hull. On sailboats, the fin or ballasted appendage that resists sideways drift.
Chine	The line where the bottom of the hull meets the sides, either a hard angle or a soft curve.
Deadrise	The angle of the hull bottom measured from horizontal, usually quoted at the transom. Higher deadrise means a softer ride in chop.
Freeboard	The height of the hull side from the waterline to the deck edge.
Bilge	The lowest interior part of the hull, where water collects and bilge pumps sit.
Bulkhead	A structural wall inside the hull that adds stiffness and can divide compartments.
Stringer	A lengthwise structural beam inside the hull bottom that carries engine and slamming loads.
Gunwale	The upper edge of the hull side, pronounced 'gunnel'.
Waterline	The line where the hull meets the water at rest.
Core	Lightweight material such as foam or balsa sandwiched between fiberglass skins. Wet core is a common survey finding.

Directions and positions aboard

Positions aboard are fixed to the boat, not to the person speaking. That is the whole point of port and starboard.

Term	Meaning
Port	The left side of the boat when facing the bow. Port running lights are red.
Starboard	The right side when facing the bow. Starboard running lights are green.
Forward	Toward the bow.
Aft	Toward the stern.
Abeam	At right angles to the boat's centerline, directly off the side.
Amidships	The middle of the boat, either lengthwise or across.
Athwartships	Running across the boat from side to side.
Astern	Behind the boat, or moving backward.
Windward	The side or direction the wind is coming from. Also called weather side.
Leeward	The side away from the wind, pronounced 'loo-ard'.
Below	Inside the boat, under the main deck.

Deck, hardware and fittings

Deck gear is where most hands-on work happens, especially when docking. Knowing these names makes you a useful crew member on any boat.

Term	Meaning
Cleat	A horn-shaped fitting that lines are secured to.
Chock	A guide on the deck edge that leads a dock or anchor line without chafe.
Windlass	A powered winch that raises and lowers the anchor.
Stanchion	A vertical post that supports lifelines or rails.
Lifeline	Wire or line strung between stanchions to keep people aboard.
Fender	A cushion hung over the side to protect the hull at a dock.
Davit	A small crane or arm used to raise and stow a dinghy.
Swim platform	The low platform at the stern for boarding from the water or a tender.
Cockpit	The open, usually lower area aft where the crew works or relaxes.
Helm	The steering station, or the wheel itself.
T-top	A rigid sunshade on a center console supported by a frame around the helm.
Flybridge	An upper helm station and lounging deck above the main cabin.

Lines, knots and rope handling

On a boat, rope becomes a line the moment it has a job. A handful of knots covers almost every situation an owner meets.

Term	Meaning
Line	Any rope in use aboard a boat.
Bitter end	The free end of a line or the inboard end of an anchor rode.
Cleat hitch	The standard figure-eight wrap used to secure a line to a cleat.
Bowline	A knot that forms a fixed loop that will not slip or jam, easy to untie after loading.
Clove hitch	A quick hitch around a post or rail, handy for fenders.
Round turn and two half hitches	A secure knot for tying to a ring or piling under load.
Figure-eight knot	A stopper knot tied in the end of a line to keep it from running out of a block.
Bow line	The dock line led from the bow, not to be confused with the bowline knot.
Spring line	A dock line led at an angle forward or aft to stop the boat surging along the dock.
Painter	The line attached to the bow of a dinghy.
Flake	To lay a line out in loose loops so it runs freely without tangling.

Sails, rig and sail handling

Sailing has the deepest vocabulary of any part of boating. These are the terms you will see in every sailboat and catamaran review on this site.

Term	Meaning
Mast	The vertical spar that carries the sails.
Boom	The horizontal spar along the bottom of the mainsail.
Standing rigging	Fixed wires or rods that hold the mast up, including shrouds and stays.
Shrouds	Wires supporting the mast from the sides.
Forestay	The wire from the bow to the masthead or near it, on which the jib sets.
Halyard	A line that hoists a sail.
Sheet	A line that trims a sail in or out.
Mainsail	The principal sail set behind the mast.
Jib	A triangular headsail set forward of the mast. A large overlapping jib is a genoa.
Spinnaker	A large, light, balloon-shaped sail for downwind sailing. An asymmetric version is often called a gennaker.
Furler	A system that rolls a sail around a stay or inside the mast or boom to set and stow it.
Reef	To reduce sail area as the wind builds.
Winch	A drum with a handle or motor that gives mechanical advantage on sheets and halyards.
Tack	To turn the bow through the wind. Also the lower forward corner of a sail.
Jibe	To turn the stern through the wind, swinging the boom across.
Close-hauled	Sailing as close to the wind as the boat can efficiently point.
Luff	The forward edge of a sail, or the flapping of a sail that is not trimmed in enough.
Heel	The sideways lean of a sailboat under wind pressure.
Weather helm	The tendency of a sailboat to turn into the wind, felt as pressure on the wheel or tiller.

Engines, drives and hull behavior

Powerboat reviews revolve around these words. Understanding how drive type and hull form interact is the key to reading performance numbers honestly.

Term	Meaning
Outboard	A self-contained engine and drive unit clamped to the transom or a bracket.
Sterndrive	An inboard engine linked through the transom to a steerable drive leg, also called inboard-outboard.
Pod drive	A steerable drive unit mounted under the hull, such as Volvo Penta IPS or Cummins Zeus, usually with joystick control.
Shaft	The rotating rod that carries power from the gearbox to the propeller.
Pitch	The theoretical distance a propeller advances in one revolution. Also the bow-up, bow-down motion of a boat.
Trim tabs	Adjustable plates at the transom that change running attitude and correct list.
Planing hull	A hull designed to rise up and skim on top of the water at speed.
Displacement hull	A hull that pushes through the water and is limited to roughly its hull speed.
Semi-displacement	A hull that can exceed hull speed with more power but does not fully plane efficiently.
Hull speed	The practical top speed of a displacement hull, about 1.34 times the square root of waterline length in feet, in knots.
Bow thruster	A small propeller in a tunnel near the bow that pushes the bow sideways for docking.
Joystick	A single control that coordinates engines, drives and thrusters to move the boat in any direction.
Gyrostabilizer	A spinning flywheel unit, such as a Seakeeper, that reduces rolling at rest and underway.
Raw-water impeller	The rubber pump vane that draws seawater to cool the engine, a routine replacement item.

Navigation, charts and electronics

Navigation terms connect what you see on the plotter with what you see through the windshield. Several of them describe errors you must correct for.

Term	Meaning
Nautical mile	1,852 meters, about 6,076 feet, used for marine distance.
Knot	Speed of one nautical mile per hour. Never say knots per hour.
Heading	The direction the bow is pointing.
Course over ground	The actual track the boat is making over the seabed, shown as COG.
Bearing	The direction from your boat to another object.
Variation	The difference between true north and magnetic north at your location.
Deviation	Compass error caused by the boat's own metal and electronics.
Chart datum	The reference level for charted depths. US charts use mean lower low water.
Aids to navigation	Buoys, beacons, lights and daymarks that mark channels and hazards.
Nun	A red, cone-topped buoy with an even number in US waters.
Can	A green, cylindrical buoy with an odd number in US waters.
Red right returning	Keep red marks on your starboard side when returning from sea.
Chartplotter	A GPS display that shows your position on electronic charts.
AIS	Automatic Identification System, which broadcasts vessel identity, position and course.
EPIRB	Emergency position-indicating radio beacon that alerts rescuers via satellite on 406 MHz.
MMSI	A nine-digit identity number programmed into a DSC radio and AIS.
DSC	Digital Selective Calling, the VHF button that sends a distress alert with your position.

Rules of the road, radio calls and seamanship

These are the words that carry legal or safety weight. If a guest learns only one table, make it this one.

Term	Meaning
Navigation Rules	The US Inland Rules and international COLREGS that govern how vessels avoid collision.
Stand-on vessel	The boat that must hold its course and speed in a crossing or overtaking situation.
Give-way vessel	The boat that must take early, obvious action to keep clear.
Underway	Not anchored, made fast to shore or aground, even if drifting.
Mayday	Radio distress call for grave and imminent danger to life or vessel.
Pan-pan	Radio urgency call for a serious situation that is not yet life-threatening.
Securite	Radio safety call for navigational or weather warnings, pronounced 'say-cure-ee-tay'.
Channel 16	The VHF hailing and distress channel monitored by the Coast Guard.
Wake	The waves a boat leaves behind. Owners are legally responsible for wake damage.
No-wake zone	An area where boats must go slowly enough to make minimal wake.
Set and drift	The direction and speed of current acting on the boat.
Lee shore	A coast the wind is blowing toward, dangerous because the boat is pushed onto it.
Man overboard	The call and procedure when someone falls in, abbreviated MOB.

Docking, mooring and anchoring

Every cruising day ends at a slip, a mooring or an anchor. These terms come up at every marina office and in every anchorage.

Term	Meaning
Slip	A berth between docks or pilings where a boat ties up.
Mooring	A permanent anchor and buoy that a boat ties to.
Pennant	The short line from a mooring buoy to the boat's bow cleat.
Ground tackle	The anchor, chain, rode and related gear.
Rode	The line, chain or combination connecting the anchor to the boat.
Scope	The ratio of rode let out to water depth plus bow height. 5 to 1 or more is common for chain.
Snubber	A stretchy line attached to anchor chain to absorb shock and take load off the windlass.
Setting the anchor	Backing down gently so the anchor digs in.
Dragging	When the anchor fails to hold and the boat moves.
Med mooring	Docking stern-to a quay with an anchor or laid line holding the bow.

Weather, tides and sea state

Marine forecasts use a compact language of their own. These are the terms that decide whether a day trip goes ahead.

Term	Meaning
Fetch	The distance of open water over which wind blows and builds waves.
Swell	Long, regular waves generated by distant weather.
Chop	Short, steep wind waves, often on shallow bays and sounds.
Head sea	Waves coming from ahead.
Beam sea	Waves striking the side, the main cause of rolling.
Following sea	Waves coming from astern, which can cause broaching.
Small craft advisory	A National Weather Service alert that conditions are hazardous to small boats. Thresholds vary by region.
Beaufort scale	A 0 to 12 scale describing wind force and sea state.
Flood	The incoming, rising tidal current.
Ebb	The outgoing, falling tidal current.
Slack water	The brief period when tidal current is near zero.

Ownership, buying and accommodation

Every listing, survey report and purchase agreement uses these terms. They also appear in the spec tables on our model pages.

Term	Meaning
LOA	Length overall, the boat's full length from bow to stern.
LWL	Length at the waterline, which governs hull speed.
Beam	The boat's maximum width.
Draft	The depth from the waterline to the lowest point of the boat.
Air draft	The height from the waterline to the highest point, which decides bridge clearance.
Displacement	The weight of the boat, equal to the weight of water it displaces.
HIN	The 12-character hull identification number required on boats built in the US since 1972.
Documentation	Federal registration with the US Coast Guard, available to vessels of at least five net tons.
Survey	A professional inspection of condition and value before purchase or insurance.
Sea trial	A test run before closing to confirm the boat performs as represented.
Bareboat charter	Renting a boat without crew and skippering it yourself.
Crewed charter	Chartering a yacht with a professional captain and crew included.
Six-pack	Slang for the OUPV captain's license, allowing up to six paying passengers on an uninspected vessel.
Tender	A small boat used to get between the yacht and shore.
Head	A marine toilet or the bathroom aboard. Also the top corner of a sail.
Galley	The kitchen.
Stateroom	A private sleeping cabin.
V-berth	A V-shaped bed in the bow cabin.

Models mentioned in this guide

Catalina 30

Cruising Sailboats, 30 ft

Used $8K to $58K

Beneteau Oceanis 46.1

Cruising Sailboats, 48 ft

Used $300K to $640K

Boston Whaler 170 Montauk

Luxury Dayboats & Classics, 17 ft

Used $18K to $55K

Grady-White Express 330

Center Consoles & Offshore Boats, 34 ft

Used $65K to $560K

Sea Ray Sundancer 320

Sport Yachts & Express Cruisers, 33 ft

Used $210K to $480K

Frequently asked questions

Why do boaters say port and starboard instead of left and right?

Because port and starboard are fixed to the boat and never change with the direction a person faces. That removes confusion when crew are facing different ways.

What is the difference between a knot and a mile per hour?

A knot is one nautical mile per hour, and a nautical mile is about 6,076 feet versus 5,280 feet for a statute mile. So 20 knots is about 23 mph.

What does draft mean on a boat?

Draft is the vertical distance from the waterline to the lowest point of the hull, keel or running gear. It tells you the minimum water depth the boat needs.

What is the difference between Mayday and Pan-pan?

Mayday is for grave and imminent danger to life or the vessel. Pan-pan signals an urgent problem, such as engine failure in a shipping lane, that is not yet life-threatening.

Is a line the same as a rope?

Rope is the material. Once it has a job aboard, such as a dock line, sheet or halyard, sailors call it a line.

What does scope mean when anchoring?

Scope is the ratio of anchor rode let out to the depth of water plus the height of the bow. More scope gives a lower pull angle and better holding.

Boating Terminology, 150 Terms Every Owner Should Know