M

mainsail
The largest regular sail on a sailboat.

make fast
To secure a line.

marinization
The addition of marine components to automotive engines.

mast
Vertical spar that supports sails.

MAYDAY
A radio distress call.

megayacht
A large, luxurious yacht, typically longer than 100 feet.

midships
Location near the center of a boat.

mizzen mast
A shorter mast located aft of the main mast on a yawl or ketch.

modified-V hull
A modification of the deep-V hull shape with a deadrise of less than 20 degrees.

mold
A hollow reinforced cavity that is the mirror-image or reverse-image of the boat and into which fiberglass, gel coat and resin are laid during composite-hull construction.

monohull
A boat with a single hull.

mooring
Permanent ground tackle fixed to a buoy that boats can tie to.

motorsailer
A hybrid boat that has sails and powerful engines.

motoryacht
A large powerboat greater than 40 feet with luxurious interior accommodations for long-range cruising.

multihull
A boat with more than one hull, such as a catamaran or trimaran.