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.