flashflashflashesflashedflashing1verb (flashes, flashing, flashed)1to send out a bright light that comes and goes quickly; to make something do this: The light kept flashing on and off. She flashed her headlights at the other driver.2to appear and disappear very quickly, or to make something do this: I saw something flash past the window. They flashed the answer up on the TV screen.flashflashflashes2noun (pluralflashes)1a bright light that comes and goes quickly: a flash of lightning2a bright light that you use with a camera for taking photographsin a flashvery quickly: The weekend was over in a flash.