YPI Yachting Glossary
All the yachting terms explained...from A to Z
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
| magnetic bearing | The bearing of an object after magnetic variation has been considered, but without compensation for magnetic deviation. |
| magnetic course | The course of a vessel after magnetic variation has been considered, but without compensation for magnetic deviation. |
| magnetic deviation | Compass error. The difference between the reading of a compass and the actual magnetic course or bearing due to errors in the compass reading. These errors can be caused by metals, magnetic fields and electrical fields near the compass. Prior to using a compass, magnetic deviation should be recorded for many different points on the compass as the error can be different at different points. The act of checking for magnetic deviation is called swinging. |
| magnetic north | The direction to which a compass points. Magnetic north differs from true north because the magnetic fields of the planet are not exactly in line with the north and south poles. Observed differences between magnetic and true north is known as magnetic variation. |
| magnetic variation | The difference between magnetic north and true north, measured as an angle. Magnetic variation is different in different locations, so the nearest compass rose to each location on a chart must be used. |
| main mast | The tallest (or only) mast on a boat. |
| main sail | (mainsl') The largest sail on a multiple sail boat. |
| main sheet | Line that controls the position of the mainsail. |
| main stay | The line supporting the mast |
| main topsail | A topsail on the main mast. |
| make fast | To attach a line to something so that it will not move. |
| make way | Moving through the water. |
| marconi rig | Lightweight mast supported by stays and shrouds. |
| marina | A place where boats can find fuel, water and other services. Marinas also contain slips where boats can stay for a period of time. |
| mark | Marks used on a lead line or anchor rode indicating the length of the line at that point. A buoy or other object used to mark a location. |
| marl | To wrap a small line around another. |
| marline | A small line used for whipping, seizing, and lashing. |
| marlinespike | A pointed tool used to separate the strands of a rope or wire. |
| mast | The pole attached to the deck at the right angle, holding up the sails. |
| mast boot | A protective cover wrapped around the mast at the deck on a keel stepped boat to prevent water from entering the boat. |
| mast box | A box where a deck stepped mast is stepped. |
| mast gate | The point at which the mast enters the foredeck of a boat |
| mast head | The top of the mast. |
| mast partners | Supporting structures to take the load of the mast at the deck. |
| mast spanner | A device that allows the control of a rotating mast on catamarans |
| mast step | Fitting or construction into which the base of the mast is placed. |
| mast track | A track or groove in the back of the mast to which the sail is attached by means of lugs or the bolt rope. |
| master | The person in charge of a vessel. The captain. |
| masthead | The top of the mast. |
| masthead light | Also known as a steaming light. The masthead light is a white light that is visible for an arc extending across the forward 225° of the boat. When lit the masthead light indicates that a vessel under power, including sailboats with engines running. Masthead lights are usually located halfway up the mast rather than at the top. |
| masthead rig | A design in which the forestay runs to the peak of the mast. |
| mastman | The crewmember who works the lines on the mast when hoisting sails, and who assists the bowman with the work on the foredeck. |
| match racing | A racing format where only two yachts compete at a time |
| mate | An assistant to the captain. |
| maxi | A boat designed to the maximum rating allowed under the International Offshore Rule, or more recently, the international measurement system. |
| mayday | From the French m'aidez, a distress signal. |
| mean high water | The depth of the water at average high tide. |
| mean low water | A figure representing the average low tide of a region. |
| mean lower low water | In an area with two tides, this figure represents the average of the lowest of the low tides. |
| measured mile | A course marked by buoys or ranges measuring one nautical mile. Measured miles are used to calibrate logs. |
| meat hook | slang expression for a large fishing hook |
| mechanical advantage (or purchase) | A mechanical method of increasing an applied force. Disregarding the effects of friction, if a force of 100 pounds applied to a tackle is magnified to a force of 400 pounds, the purchase or mechanical advantage is said to befour to one, or 4: 1. |
| mediterranean berth | A method of docking with a boat's stern to the dock. |
| mercator | A type of projection of the globe used when making charts. Since the world is a sphere, it is impossible to draw accurate charts on flat paper. A Mercator projection shows all of the meridians as straight vertical lines rather than lines that would intersect. This is the type of projection used on a typical world map, but the distances become very distorted near the poles. |
| meridian | A longitude line. Meridians are imaginary circles that run through both poles. |
| messenger | A small line used to pull a heavier line or cable. The messenger line is usually easier to throw, lead through holes or otherwise manipulate than the line that it will be used to pull. |
| meteorology | The study of weather. |
| midchannel buoy | A red and white vertically striped buoy used in the United States to mark the middle of a channel. Midchannel buoys may be passed by on either side. Also see nun and can buoys. |
| midship | Center of the vessel, middle between bow and stern |
| midships | A place on a boat where its beam is the widest. |
| millibar | A unit of pressure used to measure the pressure of the atmosphere. 1 millibar equals 0.03 inches of mercury. |
| minute | When used to measure location a minute is one sixtieth of one degree. One minute of latitude is equal to one nautical mile. Each minute is divided into sixty seconds. |
| mizzen mast | A smaller aft mast on a ketch or yawl rigged boat. |
| mizzen sail | The sail on the aft mast of a ketch or yawl rigged sailboat. |
| mizzen staysail | A small sail that is sometimes placed forward of the mizzen mast. |
| monkey deck | A false deck built over a permanent deck. Often used in the bow of larger sailing ships, forward of the anchor windlass and provides a working platform around the portion of the bowsprit as it attaches to the ship. |
| monkey fist | A large heavy knot usually made in the end of a heaving line to aid in accurate throwing. |
| monohull | A boat that has only one hull, as opposed to multihull boats such as catamarans or trimarans. |
| moor, mooring | To attach a boat to a mooring, dock, post, anchor, etc. A secure place where a boat can be moored. |
| mooring buoy | A buoy marking the location of a mooring. Usually attached to an anchor by a small pendant. |
| mooring line | A line used to secure a boat to an anchor, dock, or mooring. |
| morse code | A code that uses dots and dashes to communicate by radio or signal lights. |
| motor | An engine. The act of using an engine to move a boat. |
| motor sailer | A boat designed to use its motor for significant amounts of time and use the sails less often than a normal sailboat. |
| mount | An attachment point for another object. The act of putting an object on its mount. |
| mouse | Also mousing. Tying a line so that it will not come undone, such as when attaching a line to a hook. |
| multihull | Any boat with more than one hull, such as a catamaran or trimaran. |
| mushroom anchor | A type of anchor with a heavy inverted mushroom shaped head. Mushroom anchors are used to anchor in mud and other soft ground. |