1 [no object] shine in a bright but brief, sudden, or intermittent way:lightning flashed overheadan irritating neon sign flashed on and off (as adjective flashing)a police car with a flashing light
[with object] cause to shine briefly or suddenly:the oncoming car flashed its lights
[with object] shine or show a light to send (a signal):red lights started to flash a warning
[with object] give (a swift look):Carrie flashed a glance in his direction [with two objects]:she flashed him a withering look
(of a person’s eyes) indicate sudden emotion, especially anger:she glared at him, her eyes flashing
2 [no object, with adverbial of direction] move or pass very quickly:a look of terror flashed across Kirov’s face figurativea sudden thought flashed through his mind
[with object and adverbial of direction] send (news or information) swiftly by means of telegraphy or telecommunications:the story was flashed around the world
3 [with object] display (information or an image) suddenly on a television or computer screen or electronic sign, typically briefly or repeatedly:the screen flashed up a menu
[no object] (of information or an image) be displayed briefly or repeatedly on a screen:the election results flashed on the screen
informal hold up or show (something, often proof of one’s identity) quickly before replacing it:she opened her purse and flashed her ID card
informal make a conspicuous display of (something) so as to impress or attract attention:they flashed huge wads of money about
[no object] informal (of a man) show one’s genitals briefly in public.
1a sudden brief burst of bright light:a flash of lightning
a patch or sudden display of a bright colour:the woodpecker swooped from tree to tree with a flash of yellow, green, and red
British a coloured patch of cloth on a uniform used as the distinguishing emblem of a regiment, formation, or country:a short man with the black flashes of the tank units
a coloured band on the packaging of a product used to catch the consumer’s eye:on-pack flashes offer a free ‘Taste of the Caribbean’
a pre-drawn design for a tattoo.
2a sudden or brief manifestation or occurrence of something:she had a flash of inspiration
3a camera attachment that produces a brief very bright light, used for taking photographs in poor light:an electronic flash [mass noun]:if in any doubt use flash
4 (Flash) [mass noun] Computing ( trademark in the US) a platform for producing and displaying animation and video in web browsers.
5 [mass noun] informal ostentatious stylishness or display of wealth:workwear represents a move away from Eighties designer flash
6 [mass noun] excess plastic or metal forced between facing surfaces as two halves of a mould close up, forming a thin projection on the finished object:flap wheels are ideal for grinding off fibreglass flash
7a rush of water, especially down a weir to take a boat over shallows.
informal, chiefly British
1ostentatiously stylish or expensive:a flash new car
ostentatiously displaying one’s wealth:he’s a bit flash and refers to his gold card a few times too many
2 archaic relating to the language used by criminals or prostitutes.
flash in the pan
a thing or person whose sudden but brief success is not repeated or repeatable:our start to the season was just a flash in the pan
[with allusion to priming of a firearm, the flash arising from an explosion of gunpowder within the lock]
in (or like) a flash
very quickly; immediately:she was out of the back door in a flash
(as) quick as a flash
(especially of a person’s response or reaction) very quickly:quick as a flash he was at her side
make an electric circuit by sparking across a gap.
(of a fire) spread instantly across a gap because of intense heat.
Middle English (in the sense 'splash water about'): probably imitative; compare with flush1 and splash