Mortar 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. [Slang], Mortar Mor"tar, n. [OE. morter, AS. mort[=e]re, L. mortarium: cf. F. mortier mortar. Cf. sense 2 (below), also 2d Mortar, Martel, Morter.] 1. A strong vessel, commonly in form of an inverted bell, in which substances are pounded or rubbed with a pestle. 2. [F. mortier, fr. L. mortarium mortar (for trituarating).] (Mil.) A short piece of ordnance, used for throwing bombs, carcasses, shells, etc., at high angles of elevation, as 45[deg], and even higher; -- so named from its resemblance in shape to the utensil above described. Mortar bed (Mil.), a framework of wood and iron, suitably hollowed out to receive the breech and trunnions of a mortar. Mortar boat or vessel (Naut.), a boat strongly built and adapted to carrying a mortar or mortars for bombarding; a bomb ketch. Mortar piece, a mortar. [Obs.] --Shak., Mortar Mor"tar, v. t. To plaster or make fast with mortar., Mortar Mor"tar, n. [F. mortier. See Mortar a vessel.] A chamber lamp or light. [Obs.] --Chaucer.