intransitive verb

1. to send out or reflect a sudden, brief blaze or light, esp. at intervals
2. to sparkle or gleam eyes flashing with anger
3. to speak abruptly, esp. in anger: usually with out
4. to come, move, or pass swiftly and suddenly; be seen or realized for an instant like a flash of light an idea flashed through his mind
5. Informal to expose one's genitals, breasts, etc. briefly and deliberately in public
6. Informal to have a sudden idea, thought, insight, or recollection: usually with on

Etymology: ME flashen, to splash, sprinkle; of echoic orig.

transitive verb

1. to send out (light, etc.) in sudden, brief spurts
2. to cause to flash
3. to signal with light or reflected light
4. to send (news, messages, etc.) swiftly or suddenly, as by radio
5. to put flashing on so as to make weatherproof
6. Informal to show briefly or ostentatiously to flash a roll of money
7. Informal to expose (one's genitals, breasts, etc.) briefly and deliberately to (someone)
8. Archaic to splash or dash (water)
9. Glassmaking
   1. to put (a colored film of glass) on other glass
   2. to coat with a colored film of glass

noun

1. 1. a sudden, brief light
   2. a sudden burst of flame or heat
2. a brief time; moment
3. a sudden, brief display of thought, understanding, feeling, etc. a flash of wit
4. ☆ a brief news report of something that has just happened
5. a gaudy display; showiness
6. a preparation containing burnt sugar, used for coloring liquors
7. anything that flashes; specif., an electric light source that gives a brief dazzling light for taking photographs
8. Informal
   1. a flashlight
   2. a person very quick or adept at something

adjective

1. Chiefly Brit., Informal
   1. flashy; showy; sporty
   2. of thieves or other social outcasts
2. that flashes; happening swiftly or suddenly a flash warning
3. working with a coordinated flash of light a flash camera
4. Comput. designating or of an erasable memory device that retains stored data when power is turned off