n. The top or head of the mast of a ship or vessel; technically, the top or head of the lower mast, but by extension the highest point of the mast.n. One who is stationed at the masthead: as, the sundown masthead.To raise to the masthead; place or display at the masthead.To punish, as a sailor, by sending to the masthead (the top of one of the lower masts) for a certain or an indefinite time.