v., n., & adj.
v. 1 intr. & tr. emit or reflect or cause to emit or reflect light briefly, suddenly, or intermittently; gleam or cause to gleam. 2 intr. break suddenly into flame; give out flame or sparks. 3 tr. send or reflect like a sudden flame or blaze (his eyes flashed fire). 4 intr. a burst suddenly into view or perception (the explanation flashed upon me). b move swiftly (the train flashed through the station). 5 tr. a send (news etc.) by radio, telegraph, etc. (flashed a message to her). b signal to (a person) by shining lights or headlights briefly. 6 tr. colloq. show ostentatiously (flashed her engagement ring). 7 intr. (of water) rush along; rise and flow. 8 intr. sl. indecently expose oneself.
n. 1 a sudden bright light or flame, e.g. of lightning. 2 a very brief time; an instant (all over in a flash). 3 a a brief, sudden burst of feeling (a flash of hope). b a sudden display (of wit, understanding, etc.). 4 = NEWSFLASH. 5 Photog. = FLASHLIGHT 1. 6 a a rush of water, esp. down a weir to take a boat over shallows. b a contrivance for producing this. 7 Brit. Mil. a coloured patch of cloth on a uniform etc. as a distinguishing emblem. 8 vulgar display, ostentation. 9 a bright patch of colour. 10 Cinematog. the momentary exposure of a scene. 11 excess plastic or metal oozing from a mould during moulding.
adj. colloq. 1 gaudy; showy; vulgar (a flash car). 2 counterfeit (flash notes). 3 connected with thieves, the underworld, etc. flash-board a board used for sending more water from a mill-dam into a mill-race. flash bulb Photog. a bulb for a flashlight. flash burn a burn caused by sudden intense heat, esp. from a nuclear explosion. flash card a card containing a small amount of information, held up for pupils to see, as an aid to learning. flash-cube Photog. a set of four flash bulbs arranged as a cube and operated in turn. flash-flood a sudden local flood due to heavy rain etc. flash-gun Photog. a device used to operate a camera flashlight. flashing-point = FLASHPOINT. flash in the pan a promising start followed by failure (from the priming of old guns). flash-lamp a portable flashing electric lamp. flash out (or up) show sudden passion. flash over Electr. make an electric circuit by sparking across a gap. flash-over n. an instance of this.
[ ME orig. with ref. to the rushing of water: cf. SPLASH ]