• Any protuberant part; a round, swelling part or body; a knoblike process; as, a boss of wood. • A protuberant ornament on any work, either of different material from that of the work or of the same, as upon a buckler or bridle; a stud; a knob; the central projection of a shield. See Umbilicus. • A projecting ornament placed at the intersection of the ribs of ceilings, whether vaulted or flat, and in other situations. • A wooden vessel for the mortar used in tiling or masonry, hung by a hook from the laths, or from the rounds of a ladder. • The enlarged part of a shaft, on which a wheel is keyed, or at the end, where it is coupled to another. • A swage or die used for shaping metals. • A head or reservoir of water. • To ornament with bosses; to stud. • A master workman or superintendent; a director or manager; a political dictator.