The Collaborative International Dictionary of English v.0.48:

Yowl \Yowl\, v. i. [See Yawl, v. i.]
   To utter a loud, long, and mournful cry, as a dog; to howl;
   to yell.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Yowl \Yowl\, n.
   A loud, protracted, and mournful cry, as that of a dog; a
   howl.
   [1913 Webster]

WordNet (r) 3.0 (2006):

yowl
    n 1: 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, yowl]
    v 1: cry loudly, as of animals; "The coyotes were howling in the
         desert" [syn: howl, wrawl, yammer, yowl]
    2: utter shrieks, as of cats [syn: yowl, caterwaul]