Mor″tar, n. [OE. mortier, F. mortier, L. mortarium mortar, a large basin or trough in which mortar is made, a mortar (in sense 1, above). See 1st Mortar.] (Arch.) A building material made by mixing lime, cement, or plaster of Paris, with sand, water, and sometimes other materials; — used in masonry for joining stones, bricks, etc., also for plastering, and in other ways.
Mortar bed, a shallow box or receptacle in which mortar is mixed. — Mortar board. (a) A small square board with a handle beneath, for holding mortar; a hawk. (b) A cap with a broad, projecting, square top; — worn by students in some colleges.