n. (pl. -flies) 1 any diurnal insect of the order Lepidoptera, with knobbed antennae, a long thin body, and four usu. brightly coloured wings erect when at rest. 2 a showy or frivolous person. 3 (in pl.) colloq. a nervous sensation felt in the stomach. butterfly net a fine net on a ring attached to a pole, used for catching butterflies. butterfly nut a kind of wing-nut. butterfly stroke a stroke in swimming, with both arms raised and lifted forwards together. butterfly valve a valve with hinged semicircular plates.
[ OE buttor-fleoge (as BUTTER, FLY(2)) ]