butterfly valve n 1: a valve in a carburetor that consists of a disc that turns and acts as a throttle
Butterfly \But"ter*fly`\, n.; pl. {Butterflies}. [Perh. from the color of a yellow species. AS. buter-fl[=e]ge, buttor-fle['o]ge; cf. G. butterfliege, D. botervlieg. See {Butter}, and {Fly}.] (Zool.) A general name for the numerous species of diurnal Lepidoptera. Note: [See Illust. under {Aphrodite}.] [1913 Webster] {Asclepias butterfly}. See under {Asclepias}. {Butterfly fish} (Zool.), the ocellated blenny ({Blennius ocellaris}) of Europe. See {Blenny}. The term is also applied to the flying gurnard. {Butterfly shell} (Zool.), a shell of the genus {Voluta}. {Butterfly valve} (Mech.), a kind of double clack valve, consisting of two semicircular clappers or wings hinged to a cross rib in the pump bucket. When open it somewhat resembles a butterfly in shape. [1913 Webster]