Source : Webster's Revised Unabridged Dictionary (1913)

Growl \Growl\, v. i. [imp. & p. p. {Growled}; p. pr. & vb. e.
   {Growling}.] [D. grollen to grunt, murmur, be angry; akin to
   G. grollen to be angry.]
   To utter a deep guttural sound, sa an angry dog; to give
   forth an angry, grumbling sound. --Gay.

Growl \Growl\, v. t.
   To express by growling. --Thomson.

Growl \Growl\, n.
   The deep, threatening sound made by a surly dog; a grumbling
   sound.

Source : WordNet®

growl
     n : the sound of growling (as made by animals) [syn: {growling}]
     v : to utter or emit low dull rumbling sounds; "he grumbled a
         rude response"; "Stones grumbled down the cliff" [syn: {grumble},
          {rumble}]