Source : Webster's Revised Unabridged Dictionary (1913)

Yowl \Yowl\, v. i. [See {Yawl}, v. i.]
   To utter a loud, long, and mournful cry, as a dog; to howl;
   to yell.

Yowl \Yowl\, n.
   A loud, protracted, and mournful cry, as that of a dog; a
   howl.

Source : WordNet®

yowl
     n : a very loud utterance (like the sound of an animal); "his
         bellow filled the hallway" [syn: {bellow}, {bellowing}, {holla},
          {holler}, {hollering}, {hollo}, {holloa}, {roar}, {roaring}]
     v 1: cry loudly, as of animals; "The coyotes were howling in the
          desert" [syn: {howl}, {wrawl}, {yammer}]
     2: utter shrieks, as of cats [syn: {caterwaul}]