Boss, in Architecture, a raised ornament, covering the intersections of the ribs of ceilings. They are more frequently seen in vaulted roofs, as in the aisles of a church, but occur also where the ceiling is flat. In early Norman work there are generally no bosses, and they become richer and more frequent as we advance towards the Decorated and Perpendicular styles. In the Decorated style the boss usually consists of foliage, sometimes combined with animals, heads, and the like. Coats-of-arms, charged with armorial bearings, came then also to be used for this purpose, though they were more frequent in the Perpendicular.—The boss of a bit is the ornament with which a bridle-bit terminates at each end. It was borne in the arms of the corporation of Lorimers. See LORIMER.