(verb)
to pass by very quickly, or to move or be transported very quickly;
e.g. I saw a smile flash across her face. He likes to flash down the street on his bicycle.
(verb)
to be displayed suddenly and often briefly somewhere, especially on a screen such as a computer or TV;
e.g. We waited for the election outcome to flash onto the screen.
(noun)
a sudden glint or bright light that shines briefly, especially after reflecting off of some surface;
e.g. We saw a flash of lightning before we heard the thunder.
(noun)
a sudden outburst, occurrence, or instance of an emotion, understanding, or quality;
e.g. He snapped at them in a flash of temper which he regretted later.
(noun)
an attachment or feature on many cameras that provides a brief, sudden, but very bright light and is used when taking pictures in poor/dim lighting;
e.g. I turned on the flash so that the photograph wouldn't appear shadowy.