[plinth] n [L plinthus, fr. Gk plinthos] (1601) 1 a: the lowest member of a base: subbase b: a block upon which the moldings of an architrave or trim are stopped at the bottom
2: a usu. square block serving as a base; broadly: any of various bases or lower parts--see base illustration
3: a course of stones forming a continuous foundation or base course