(1):

(n.) A pole, or long, strong, round piece of timber, or spar, set upright in a boat or vessel, to sustain the sails, yards, rigging, etc. A mast may also consist of several pieces of timber united by iron bands, or of a hollow pillar of iron or steel.

(2):

(n.) The vertical post of a derrick or crane.

(3):

(n.) A spar or strut to which tie wires or guys are attached for stiffening purposes.

(4):

(v. t.) To furnish with a mast or masts; to put the masts of in position; as, to mast a ship.

(5):

(n.) The fruit of the oak and beech, or other forest trees; nuts; acorns.