(a corruption of bulge, from Fr. bouge, Lat. bulga, a bag, deriving probably from an original Celtic word), the "belly" or widest part of a cask; the broad horizontal part of a ship's bottom above the keel; also the lowest interior part of the hull; hence "bilge-water," the foul water which collects in the bilge. "Bilge-keels" are pieces of timber fastened to the bottom of a ship to reduce rolling (see Shipbuilding).