M

Main mast
The tallest (possibly only) mast on a boat.

Mainsail
The main sail that is suspended from the main mast.

Main sheet
The line used to control the mainsail.

Main topsail
A topsail on the main mast.

Make fast
To attach a line to something so that it will not move.

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.

Mast
Any vertical pole on the boat that sails are attached to. If a boat has more than one mast, they can be identified by name.

Master
The person in charge of a vessel. The captain.

Masthead
The top of a mast.

Mate
An assistant to the captain.

Mayday
An internationally recognized distress signal used on a radio to indicate a life-threatening situation. Mayday calls have priority over any other radio transmission and should be used only if there is an immediate threat to life or vessel. More urgent than a pan pan or securite call.

Meridian
A longitude line. Meridians are imaginary circles that run through both poles.

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.

Monohull
A boat that has only one hull, as opposed to multihull boats such as catamarans or trimarans.

Moor
To attach a boat to a mooring, dock, post, anchor, etc.

Mooring
A place where a boat can be moored. Usually, a buoy marks the location of a firmly set anchor.

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
1) An engine. 2) 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
1) An attachment point for another object. 2) The act of putting an object on its mount.

Multihull
Any boat with more than one hull, such as a catamaran or trimaran.