whis·tle 
(wĭsəl, hwĭs-)
(wĭsəl, hwĭs-)v. whis·tled, whis·tling, whis·tles
v.intr.
1. To produce a clear musical sound by forcing air through the teeth or through an aperture formed by pursing the lips.
2. To produce a clear, shrill, sharp musical sound by passing air over or through an opening: The tea kettle whistled on the stove.
3.
a. To produce a high-pitched sound when moving swiftly through the air: The stone whistled past my head.
b. To produce a high-pitched sound by the rapid movement of air through an opening or past an obstruction: Wind whistled through the cracks in the windows.
4. To emit a shrill, sharp, high-pitched cry, as some birds and other animals.
v.tr.
1. To produce by whistling: whistle a tune.
2. To summon, signal, or direct by whistling: I whistled down a cab. The referee whistled that the play was dead.
3. Sports To signal a rule infraction committed by (a player).
n.
Idioms: 1.
a. A small wind instrument for making whistling sounds by means of the breath.
b. A device for making whistling sounds by means of forced air or steam: a factory whistle.
2. A sound produced by a whistling device or by whistling through the lips.
3. A whistling sound, as of an animal or projectile.
blow the whistle Slang
To expose a wrongdoing in the hope of bringing it to a halt: an attorney who blew the whistle on governmental corruption.
whistle in the dark
To attempt to keep one's courage up.
[Middle English whistlen, from Old English hwistlian.]