the fruit of the oak and beech, or other forest trees; nuts; acorns.-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.-the vertical post of a derrick or crane.-to furnish with a mast or masts; to put the masts of in position; as, to mast a ship.