Whistle

to make a clear musical sound, a series of such sounds, or a high-pitched, warbling sound by the forcible expulsion of the breath through a small opening formed by contracting the lips, or through the teeth, with the aid of the tongue.
to make such a sound or series of sounds otherwise, as by blowing on some device.
to emit similar sounds from the mouth, as birds do.
(of a device) to produce a similar sound when actuated by steam or the like:
This teakettle whistles when it boils.
to move, go, pass, etc., with a whistling or whizzing sound, as a bullet or the wind.
to produce by whistling:
to whistle a tune.
to call, direct, or signal by or as by whistling:
He whistled his dog over.
to send with a whistling or whizzing sound.
an instrument for producing whistling sounds by means of the breath, steam, etc., as a small wooden or tin tube, a pipe, or a similar device with an air chamber containing a small ball that oscillates when air is forced through an opening, producing a high-pitched, warbling tone.
a sound produced by whistling:
a prolonged whistle of astonishment.
a simple fipple flute.
whistle for, to demand or expect without success:
After promising to pay, he told us we could whistle for our money.
blow the whistle, to expose the existence of mischief or wrongdoing:
The agent was taking bribes until someone finally blew the whistle.
blow the whistle on,

to bring a stop to; halt:
Congress has blown the whistle on all unnecessary expenditures for the program.
to expose (wrongdoing or wrongdoers):
to blow the whistle on corruption in high places.

wet one’s whistle, Informal. to take a drink.
whistle in the dark, to attempt to summon up one’s courage or optimism in a difficult situation:
He says his business will improve next year, but he’s probably just whistling in the dark.
Contemporary Examples

Anti-Vaxxers Have a New Hero Russell Saunders August 31, 2014
Fitness Gadgets … for Your Dog Megan Humphreys February 17, 2014
Fitness Gadgets … for Your Dog Megan Humphreys February 17, 2014
Justin Bieber Busted for Pot: Does It Matter? Kevin Fallon April 24, 2013
Crushing Christmas: How to Win Every Argument Kelly Williams Brown December 23, 2013

Historical Examples

The Duke Of Chimney Butte G. W. Ogden
Brave and Bold Horatio Alger
Dan Carter and the Cub Honor Mildred A. Wirt
A Rill from the Town Pump (From “Twice Told Tales”) Nathaniel Hawthorne
Old Farm Fairies: Henry Christopher McCook

verb
to produce (shrill or flutelike musical sounds), as by passing breath through a narrow constriction most easily formed by the pursed lips: he whistled a melody
(transitive) to signal, summon, or command by whistling or blowing a whistle: the referee whistled the end of the game
(of a kettle, train, etc) to produce (a shrill sound) caused by the emission of steam through a small aperture
(intransitive) to move with a whistling sound caused by rapid passage through the air
(of animals, esp birds) to emit (a shrill sound) resembling human whistling
whistle in the dark, to try to keep up one’s confidence in spite of fear
noun
a device for making a shrill high-pitched sound by means of air or steam under pressure
a shrill sound effected by whistling
a whistling sound, as of a bird, bullet, the wind, etc
a signal, warning, command, etc, transmitted by or as if by a whistle
the act of whistling
(music) any pipe that is blown down its end and produces sounds on the principle of a flue pipe, usually having as a mouthpiece a fipple cut in the side
(informal) wet one’s whistle, to take an alcoholic drink
(usually foll by on) (informal) blow the whistle

to inform (on)
to bring a stop (to)

v.
n.

whistle Dixie
whistle for
whistle in the dark