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.