| Term | Definition |
| Abaft |
Behind you when you are facing forward. |
| ABYC |
American Boat and Yacht Council, Inc. |
| Admiralty law |
The law of the sea; maritime law according to the British Admiralty. |
| Adrift |
Floating without mooring or direction. |
| Afloat | On the water. |
| Aft |
Describing the after section of a vessel, or things to the rear of amidships and near the stern. |
| Aground | Touching bottom. |
| Amidships |
In the center, the center portion of a vessel. |
| Anchor |
A forging or casting shaped to grip the sea bottom and, by means of a cable or rope, hold a boat in a desired position. |
| Anchorage | A customary, suitable and (usually) designated harbor area in which vessels may anchor. |
| Astern |
The direction toward the stern, or the back end, of the vessel. |
| Athwart |
Anything running across the boat from side to side. An aft bench seat across the stern is athwartships. |
| Aweigh |
What an anchor is when it is off the bottom. |
| Bail | To remove water from a boat by pump or bailer. |
| Bar |
A shoal of sand or mud on which you can run aground. |
| Beacon | A post or buoy placed over a shoal or bank to warn vessels, also a signal mark on land. |
| Beam |
Imaginary line amidships at right angles to keel of vessel. Also vessel’s width amidships. |
| Bearing |
The direction or point of the compass in which an object is seen. |
| Bilge |
The lower internal part of a boat’s hull. |
| Bimini |
A rectangular canopy, usually of canvas, on a light frame that protects the bridge and/or control console from sun and rain. |
| Bow | The forward part or front of the boat. |
| Bridge |
The control station from which a large boat is navigated. |
| Bulkhead | Vertical partition in a boat. |
| Buoy |
A floating object showing navigation channels or marking prohibited areas on the water. |
| Burdened vessel |
Former term for the vessel which must stay clear of vessels with the right-of-way. |
| Capsize |
To turn over, bottom side up. |
| Carburetor Backfire Flame Arrestor |
Required equipment on all motorboats except outboards and diesels. Reduces chance of fire caused by backfires in internal combustion engines. |
| Cast off |
To undo all mooring lines in preparation for departure. |
| Chart | A map of a body of water that contains piloting information. |
| Chine | The intersection of sides and bottom of a boat. |
| Chop |
Short, steep waves in an abrupt motion. |
| Cleat |
A piece of wood or metal with projecting ends to which lines are made fast. |
| Cockpit |
A well or sunken space in the afterdeck of a small boat for the use of the helmsman and crew. |
| Cockpit sole |
The floor of the cockpit. |
| Companionway |
A hatch or entrance from the deck to the cabin. |
| Compass | The instrument which shows the heading of a vessel. |
| Current |
The movement of the water in a horizontal direction. |
| Davit |
A crane that projects over the side or stern of a ship and is used as a hoist. |
| Dead ahead |
In a direction exactly ahead. |
| Deadrise | The rise on the bottom of a midships frame from the keel to the bilge. |
| Depth Sounder |
An electronic depth-finding instrument, measuring the time a sound wave takes to go from the vessel to the bottom and return, then displaying the result in feet, fathoms, or meters. |
| Dinghy |
A small boat used as a tender. |
| Displacement Hull |
Type of hull that plows through the water even when more power is added. |
| Downwind |
A direction to leeward, with the wind. |
| Draft |
The depth of the vessel below the water line, measured vertically to the lowest part of the hull. |
| Dunnage | Mats, boughs, pieces of wood, or other loose materials placed under or among goods carried as cargo in the hold of a ship to keep them dry and to prevent their motion and chafing; cushioning or padding used in a shipping container to protect fragile articles against shock and breakage; baggage or personal effects. |
| Ebb |
An outgoing tide. |
| Fathom |
A nautical linear measurement equal to 6 feet, used for measuring water depth. |
| Fenders | Objects placed along the side of the boat to protect the hull from damage. |
| Flare | The outward spread of the boat’s sides from the waterline to the rail at the bow. Also, a pyrotechnic signaling device that can indicate distress. |
| Following sea |
Waves from astern. |
| Fore |
Located at the front of the vessel; forecabin is toward the bow, the opposite of aft cabin; foredeck is the forward part of the main deck. |
| Forward | Toward the bow. |
| Founder |
To sink below the surface of the water. |
| Freeboard |
The vertical distance measured on a boat’s side from the waterline to the gunwafe. |
| Galley |
The kitchen area of a boat. |
| Give-way vessel |
The one which must stay clear of vessels which have the right-of-way. |
| Gunwale |
The upper edge of a boat’s side – pronounced “gunnel.” |
| Hail |
A call to another vessel. |
| Harbor |
A safe, protected anchorage for docking and loading. |
| Hatch |
An opening in the boat’s deck for persons or cargo to go below. |
| Head |
A marine toilet. |
| Head sea |
Waves coming from the direction in which a vessel is heading. |
| Heading |
The compass direction in which a vessel is pointed at any given moment. |
| Helm |
The wheel or tiller by which a ship is steered. |
| High tide |
High water, the highest normal level reached. |
| Holding Tank |
Storage tank for sewage, so that it will not be pumped overboard into the water. |
| Hull |
The main structural body of a vessel, excluding superstructure, masts, sails or rigging. |
| Inboard |
More toward the center of a vessel; inside; a motor fitted inside the boat. |
| Inland Rules |
Rules of the road that apply to vessel operation in harbors and certain rivers, lakes, and inland waterways. |
| Intracoastal Waterways |
ICW: bays, rivers and canals along the coasts (such as Atlantic and Gulf of Mexico coasts), connected so that vessels may travel without going into the open sea. |
| Jetty |
A structure projecting out from the shore to influence the current or tide or protect a harbor. |
| Keel |
The main structural member of a vessel, the backbone; the lateral area beneath the hull to provide steering stability and reduce leeway. |
| Knot |
To bend a line. Also, a unit of speed equal to one nautical mile (6,076.10 feet) an hour. |
| Latitude |
Geographic distance north or south of the equator. |
| Launch |
(1) To put a vessel into the water; (2) a small open powerboat, mainly used for transportation between a vessel and shore. |
| Lee | The side opposite to that from which the wind blows. |
| Leeward | Situated on the side turned away from the wind. (Opposite of windward.) |
| Limber Holes |
Drainage holes in the bilge timbers of a vessel, allowing water to run to a low point for pumping out. |
| Line |
A rope used aboard a ship. |
| List |
A continuous leaning to one side, often caused by imbalance in stowage or wind. |
| LOA | Length over all; the maximum length of a vessel’s hull, excluding projecting spars or rudder. |
| Locker | A storage place, a closet. |
| Locker |
A compartment for onboard stowage of articles. |
| Log | A record or diary of a vessel’s journey. |
| Longitude |
Geographic distance east or west of the prime meridian. |
| Lubber’s Line |
A mark or permanent line on a compass that shows the course of the boat. |
| Making Way |
Making progress through the water. |
| Marina |
A place providing secure moorings for pleasure boats and usually offering service facilities, such as fuel docks and showers. |
| Mayday |
A radio distress call, from the French m’aidez (help me); SOS in Morse Code. |
| Midships |
The center of the boat. |
| Moored |
Anchored or made fast to a pier or wharf. |
| Mooring |
Permanent ground tackle; a place where vessels are kept at anchor. |
| Nautical Mile |
6076.12 feet, or 1852 meters, an international standard; the geographical mile, the length of one minute of latitude at the equator, is 6087.20 feet. |
| Navigation Rules |
The U.S. “Rules of the Road” governing navigation lights, vessels meeting or passing, sound signals, distress signals and practical boating etiquette. |
| Offshore |
Out of sight of land. |
| Outboard |
Powerboat having an engine outside the hull. |
| Outdrive | A propulsion system for boats, with an inboard motor operating an exterior drive, with drive shaft, gears, and propeller; also called stern-drive and inboard/outboard. |
| PFD |
Personal Flotation Device; a life preserver. |
| Pier |
A structure extending into navigable water, used as a landing place or promenade. |
| Pitch | (1) The up and down movement as the bow and stern rise and fall due to wave action; (2) The theoretical distance advanced by a propeller in one revolution. |
| Planing Hull |
Type of hull that is shaped to lift out of the water at high speed and ride on the surface. |
| Port |
The left side of the boat when you are facing the bow, also a destination or harbor. |
| Privileged vessel |
Former term for the vessel with the right-of-way. |
| Propeller | Wheel or screw. Mechanism that pushes water aft to propel the boat. |
| Pulpit |
The forward railing structure at the bow. |
| Relative bearing |
A direction in relation to the fore-and-aft line of a vessel. |
| Rules of the Road |
The nautical traffic rules for preventing collisions on the water. |
| Scope | The length of the anchor rope or chain. 6 to 1 scope means that the length of the anchor rope from the boat to the anchor is 6 times the depth of the water. |
| Scupper |
A hole allowing water to run off the deck. |
| Seacock | A through-hull valve, a shut-off on a plumbing or drain pipe between the vessel’s interior and the sea. |
| Seakindly |
Comfortable in rough seas. |
| Seaworthy |
Fit or safe for a sea voyage. |
| Slip |
A berth for a boat, usually between two piers. |
| Stand-on vessel |
The vessel with the right-of-way. |
| Starboard |
The right side of the boat when you are facing the bow; a direction to the right. It is said that when navigation was guided by the stars, the constellations were displayed on “star boards” which were always placed on the right side of the pilothouse. |
| Stern |
The after end or back of the bow. |
| Stow |
To put in the proper place. |
| Swamp |
To fill with water coming in over the deck and gunwales. |
| Tender |
A dinghy or other small boat which accompanies or attends a larger vessel, such as a yacht, and is used to transport persons and provisions. |
| Transom |
The transverse planking which forms the afterend of a small, square-ended boat. (Outboard motors are usually attached to a transom.) |
| Trim | To arrange weights in a vessel in such a manner as to obtain a desired draft at bow and stern. |
| Trim tabs |
Adjustable rectangular control flaps that project along the water’s surface at the transom when the hull is planing. |
| Underway | Vessel in motion, for example, when not moored, at anchor or aground. |
| USCG |
United States Coast Guard. |
| USPS | United States Power Squadron, a private membership organization that specializes in boating education and good boating practices. |
| Vessel | Every kind of watercraft, other than a seaplane on the water, capable of being used as a means of transportation on the water. |
| VHF Radio |
A Very High Frequency electronic communications and direction finding system. |
| Wake |
Moving waves, created by vessel motion. Track or path that a boat leaves behind it, when moving across the water. |
| Wash |
The broken water left behind a speeding vessel. The surging action of the waves in the wash of a large boat can be very powerful. |
| Way or Underway |
Movement of a vessel through the water. Technically it is underway when not at anchor, aground, or made fast to the shore. The common usage is interpreted as progress through the water. Headway when going forward and Sternway when going backwards. |
| Weigh |
To raise the anchor in preparation for departure. |
| Whistle Signal |
A standard communication signal between boats, to indicate change of course, danger, or other situations. |
| Windward | Situated on the side closest to the wind. (Opposite of leeward.) |
| Yaw |
To swing erratically off course. |
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