A Mast

1. (nautical, communication, aviation) A tall, slim post or tower, usually tapering upward, used to support, for example, sails or observation platforms on a ship, the main rotor of a helicopter, flags, floodlights, meteorological instruments, or communications equipment, such as an aerial, usually supported by guy-wires (except in the case of a helicopter). [from 9th c.]
2. (naval) A non-judicial punishment ("NJP"); a disciplinary hearing under which a commanding officer studies and disposes of cases involving those under his command. [from 17th c.]

To Mast

To supply and fit a mast to (a ship). [from 16th c.]

To Demast

1. (transitive) To remove the mast from (a sailing ship) for storage.
2. (transitive) To break the mast of (a sailing ship) in an accident.

To Dismast

(transitive, nautical) To break off the mast (of a ship), especially by gunfire.