Source : Webster's Revised Unabridged Dictionary (1913)

Whistle \Whis"tle\, v. i. [imp. & p. p. {Whistled}; p. pr. & vb.
   n. {Whistling}.] [AS. hwistlian; akin to Sw. hvissla, Dan.
   hvisle, Icel. hv[=i]sla to whisper, and E. whisper. [root]43.
   See {Whisper}.]
   1. To make a kind of musical sound, or series of sounds, by
      forcing the breath through a small orifice formed by
      contracting the lips; also, to emit a similar sound, or
      series of notes, from the mouth or beak, as birds.

            The weary plowman leaves the task of day, And,
            trudging homeward, whistles on the way. --Gay.

   2. To make a shrill sound with a wind or steam instrument,
      somewhat like that made with the lips; to blow a sharp,
      shrill tone.

   3. To sound shrill, or like a pipe; to make a sharp, shrill
      sound; as, a bullet whistles through the air.

            The wild winds whistle, and the billows roar.
                                                  --Pope.

Whistling \Whis"tling\,
   a. & n. from {Whistle}, v.

   {Whistling buoy}. (Naut.) See under {Buoy}.

   {Whistling coot} (Zo["o]l.), the American black scoter.

   {Whistling Dick}. (Zo["o]l.)
   (a) An Australian shrike thrush ({Colluricincla Selbii}).
   (b) The song thrush. [Prov. Eng.]

   {Whistling duck}. (Zo["o]l.)
   (a) The golden-eye.
   (b) A tree duck.

   {Whistling eagle} (Zo["o]l.), a small Australian eagle
      ({Haliastur sphenurus}); -- called also {whistling hawk},
      and {little swamp eagle}.

   {Whistling plover}. (Zo["o]l.)
   (a) The golden plover.
   (b) The black-bellied, or gray, plover.

   {Whistling snipe} (Zo["o]l.), the American woodcock.

   {Whistling swan}. (Zo["o]l.)
   (a) The European whooper swan; -- called also {wild swan},
       and {elk}.
   (b) An American swan ({Olor columbianus}). See under {Swan}.
       

   {Whistling teal} (Zo["o]l.), a tree duck, as {Dendrocygna
      awsuree} of India.

   {Whistling thrush}. (Zo["o]l.)
   (a) Any one of several species of singing birds of the genus
       {Myiophonus}, native of Asia, Australia, and the East
       Indies. They are generally black, glossed with blue, and
       have a patch of bright blue on each shoulder. Their note
       is a loud and clear whistle.
   (b) The song thrush. [Prov. Eng.]

Source : WordNet®

whistling
     n 1: the sound made by something moving rapidly or by steam
          coming out of a small aperture [syn: {whistle}]
     2: the act of whistling a tune; "his cheerful whistling
        indicated that he enjoyed his work"
     3: the act of signalling (e.g., summoning) by whistling or
        blowing a whistle; "the whistle signalled the end of the
        game" [syn: {whistle}]