• A loose garment to be worn over other garments; an enveloping robe; a cloak. Hence, figuratively, a covering or concealing envelope. • Same as Mantling. • The external fold, or folds, of the soft, exterior membrane of the body of a mollusk. It usually forms a cavity inclosing the gills. See Illusts. of Buccinum, and Byssus. • Any free, outer membrane. • The back of a bird together with the folded wings. • A mantel. See Mantel. • The outer wall and casing of a blast furnace, above the hearth. • A penstock for a water wheel. • To cover or envelop, as with a mantle; to cloak; to hide; to disguise. • To unfold and spread out the wings, like a mantle; -- said of hawks. Also used figuratively. • To spread out; -- said of wings. • To spread over the surface as a covering; to overspread; as, the scum mantled on the pool. • To gather, assume, or take on, a covering, as froth, scum, etc.