post #1213133 post #1089577 post #506529

An instrument which produces sound from a stream of gas, most commonly air. It may be mouth-operated, or powered by air pressure, steam, or other means. Whistles vary in size from a small slide whistle or nose flute type to a large multi-piped church organ.

On this site, it's mostly used by coaches, lifeguards and referees.

Not to be confused with the action of whistling.