English Reference
noun · verb · adjective

flash

n. · v. · adj.
US /ˈfɫæʃ/ UK /flˈæʃ/ flash UK spelling flashed, flashes

  1. 01 A2 Elementary

    n.a sudden, brief, and bright light.

    n.a sudden and brief emission of light, often intense in nature.

    Simple

    A flash of lightning lit up the dark sky for a second.

    In context

    The sudden flash of the explosion was visible from several miles away, momentarily blinding the observers.

  2. 02 B1 Intermediate Photography

    n.a small light on a camera that makes a bright burst to help take photos in the dark.

    n.an electronic device or bulb used in photography to produce a brief, intense light for illumination.

    Simple

    Don't use the flash in the museum because it might damage the old paintings.

    In context

    The photographer adjusted the external flash to bounce the light off the ceiling, creating a softer effect for the portrait.

  3. 03 B1 Intermediate

    n.a very short period of time.

    n.an extremely brief interval of time; often used in the phrase 'in a flash'.

    Simple

    The summer holidays seemed to go by in a flash.

    In context

    The entire sequence of events occurred in a flash, leaving the witnesses struggling to recall the exact order of the accident.

  4. 04 B2 Upper Intermediate

    n.a sudden and powerful thought or emotion.

    n.a sudden and brilliant burst of an abstract quality, such as wit, genius, or insight.

    Simple

    I had a flash of inspiration and finally solved the puzzle.

    In context

    In a rare flash of genius, the engineer proposed a solution that bypassed the structural limitations of the original design.

  5. 05 B1 Intermediate

    v.to shine with a bright light for a very short time.

    v.to emit a brief or intermittent light; can be transitive or intransitive.

    Simple

    The lighthouse flashed its warning across the stormy sea.

    In context

    The diamond flashed brilliantly as she moved her hand under the gallery spotlights.

  6. 06 B2 Upper Intermediate

    v.to move very fast past someone or something.

    v.to move at great speed in a specified direction.

    Simple

    A red sports car flashed past us on the motorway.

    In context

    The high-speed train flashed through the station without stopping, creating a powerful gust of wind on the platform.

  7. 07 B2 Upper Intermediate

    v.to show something to someone very quickly.

    v.to make something visible for a very brief duration, often to prove identity or status.

    Simple

    The officer flashed his badge and asked to enter the building.

    In context

    He flashed a quick smile of encouragement before stepping onto the stage to begin his presentation.

  8. 08 C1 Advanced Technical Computing

    v.to update the software on a piece of hardware, like a phone or computer part.

    v.to overwrite or update the firmware in a non-volatile memory chip.

    Simple

    You need to flash the latest BIOS to support the new processor.

    In context

    The technician warned that if the power failed while flashing the firmware, the device could become permanently unusable.

    updatereprogram
  9. 09 B2 Upper Intermediate British EnglishInformal

    adj.looking expensive and impressive, often in a way that tries to get attention.

    adj.ostentatiously expensive or stylish; intended to impress others.

    Simple

    He drives a flash car but he doesn't have much money in the bank.

    In context

    The new nightclub was a bit too flash for my taste, with gold-plated fixtures and overpriced cocktails.

    showyfancyostentatious

Usage flash flooding · flash floods

If you have deeper sleep after using antihistamines, perhaps hot flashes won’t wake you up during the night, and your mood could be better the next day, she says.

The Guardian· 14 Aug 2026

In some smoke-affected thunderstorms , positive flashes accounted for more than 40% of all cloud-to-ground lightning.

The Conversation· 30 Jul 2026

Etymology 1

In some senses, from Middle English flasshen, a variant of flasken, flaskien (“to sprinkle, splash”), which was likely of imitative origin; in other senses probably of North Germanic origin akin to Swedish dialectal flasa (“to burn brightly, blaze”), related to flare. Compare also Icelandic flasa (“to rush, go hastily”).

Etymology 2

From Middle English flashe, flaske, also found as flosche and flushe (whence modern English flosh and flush), used in Middle and modern English for bodies of water with varying emphasis on them being "pools" or "marshes". It is not entirely clear whether these constitute a single term with varied spellings, or have distinct etymologies. The form flash, flashe is often suggested to be from Old French flache, French flaque, which is of Germanic origin, akin to Middle Dutch vlacke (“an estuary, flats with stagnant pools”). See flush for more on that form.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Middle English flasshen
Level B2 · Upper Intermediate
Frequency Common
Updated