"showy, cheaply attractive," 1680s, from flash (n.1) + -y (2). Earlier it meant "splashing" (1580s); "sparkling, giving off flashes" (c. 1600), but those senses have become rare. Related: Flashily; flashiness.
a flashy ring
flashback
flasher
flashing
flashlight
flash-point
flashy
flask
flat
flat-boat
flat-car
flatfish