Other forms: flashes, flashing, flashed
A flash is a burst of light that is there and gone. Lightning across a bedroom window, a camera going off at the far end of a hall, a torch swept once across a dark garden.
The verb goes everywhere. Lights flash, drivers flash their headlights, a name flashes up on a screen, a memory flashes through your mind, and somebody flashes a smile at you across a room. In a flash means instantly; a flash in the pan is a success that never happens twice; a flash flood arrives with no warning and leaves as fast. On a camera the flash is both the burst and the small unit that makes it. In British English flash is an informal adjective for showy and expensive — a flash car, a flash watch — while flashy does the same job everywhere else.
1nounflashA sudden short burst of light.
“A flash lit the whole field for half a second, then the thunder came.”
2noundeviceThe device on a camera that produces a burst of light.
“The photo came out dark because the flash did not fire.”
3verbshineTo shine suddenly and briefly, or to make a light do this.
“The lorry flashed its lights to let us pull out.”
4nounexperienceA sudden short experience of a feeling or idea.
“In a flash of temper he said something he regretted for years.”
5verbappearTo appear for a moment and then be gone.
“Her name flashed up on the screen and vanished before he could read it.”
6adjectiveshowyShowy in a way that draws attention to money. Informal, British English.
“He turned up in a flash car with the roof down.”
Too few real examples of this word to estimate which sense is commonest.
Flash has two sources tangled together. Some senses come from Middle English flasshen, a variant of flaskien, to sprinkle or splash, which was probably made from the sound itself. Others look Scandinavian, close to Swedish dialect flasa, to burn brightly or blaze. Splash and blaze both still live inside the modern word.
Middle English
flasshen
English
flasshen
English, today
flash
Built from
From English flasshen. In some senses, from Middle English flasshen, a variant of flasken, flaskien (“to sprinkle, splash”), which was likely of imitative of the sound origin; in other senses probably of gmq origin akin to Swedish dialectal flasa (“to burn brightly, blaze”), related to flare. Compare also Icelandic flasa (“to rush, go hastily”).
Etymology from Wiktionary, CC BY-SA