Source : Webster's Revised Unabridged Dictionary (1913)

Howl \Howl\, v. i. [imp. & p. p. {Howled}; p. pr. & vb. n.
   {Howling}.] [OE. houlen, hulen; akin to D. huilen, MHG.
   hiulen, hiuweln, OHG. hiuwil[=o]n to exult, h?wo owl, Dan.
   hyle to howl.]
   1. To utter a loud, protraced, mournful sound or cry, as dogs
      and wolves often do.

            And dogs in corners set them down to howl.
                                                  --Drayton.

            Methought a legion of foul fiends Environ'd me
            about, and howled in my ears.         --Shak.

   2. To utter a sound expressive of distress; to cry aloud and
      mournfully; to lament; to wail.

            Howl ye, for the day of the Lord is at hand. --Is.
                                                  xiii. 6.

   3. To make a noise resembling the cry of a wild beast.

            Wild howled the wind.                 --Sir W.
                                                  Scott.

   {Howling monkey}. (Zo["o]l.) See {Howler}, 2.

   {Howling wilderness}, a wild, desolate place inhabited only
      by wild beasts. --Deut. xxxii. 10.

Howl \Howl\, v. t.
   To utter with outcry. ``Go . . . howl it out in deserts.''
   --Philips.

Howl \Howl\, n.
   1. The protracted, mournful cry of a dog or a wolf, or other
      like sound.

   2. A prolonged cry of distress or anguish; a wail.

Source : WordNet®

howl
     n 1: a long loud emotional utterance; "he gave a howl of pain";
          "howls of laughter"; "their howling had no effect" [syn:
           {howling}, {ululation}]
     2: the long plaintive cry of a hound or a wolf
     3: a loud sustained noise resembling the cry of a hound; "the
        howl of the wind made him restless"
     v 1: emit long loud cries; "wail in self-pity"; "howl with
          sorrow" [syn: {ululate}, {wail}, {roar}, {yawl}]
     2: cry loudly, as of animals; "The coyotes were howling in the
        desert" [syn: {wrawl}, {yammer}, {yowl}]
     3: make a loud noise, as of wind, water, or vehicles; "The wind
        was howling in the trees"; "The water roared down the
        chute" [syn: {roar}]
     4: laugh unrestrainedly and heartily [syn: {roar}]