n. In architecture: The lower division of an entablature; that member which rests immediately on the column and supports those portions of the structure which are above it. See cut under entablature.n. The ornamental molding running round the extrados of an arch. Also called archivolt.n. Sometimes, less properly, the molded enrichments on the faces of the jambs and lintel of a door, window, or other opening. Also called antepagment.n. In fortification, the master-beam, or chief supporter, in any part of a subterranean fortification.