a composition, as of lime or gypsum, sand, water, and sometimes hair or other fiber, applied in a pasty form to walls, ceilings, etc., and allowed to harden and dry.
Origin: before 1000; Middle English, Old English < Medieval Latin plastrum plaster (both medical and building senses), aphetic variant of Latin emplastrum < Greek émplastron salve, alteration of émplaston, neuter of émplastos daubed; see em-2, -plast