The Collaborative International Dictionary of English v.0.48:

Bleat \Bleat\, v. i. [imp. & p. p. Bleated; p. pr. & vb. n.
   Bleating.] [OE. bleten, AS. bl?tan; akin to D. blaten,
   bleeten, OHG. bl[=a]zan, pl[=a]zan; prob. of imitative
   origin.]
   To make the noise of, or one like that of, a sheep; to cry
   like a sheep or calf.
   [1913 Webster]

         Then suddenly was heard along the main,
         To low the ox, to bleat the woolly train. --Pope
   [1913 Webster]

         The ewe that will not hear her lamb when it baas, will
         never answer a calf when he bleats.      --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bleat \Bleat\, n.
   A plaintive cry of, or like that of, a sheep.
   [1913 Webster]

         The bleat of fleecy sheep.               --Chapman's
                                                  Homer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bleat
    n 1: the sound of sheep or goats (or any sound resembling this)
    v 1: talk whiningly
    2: cry plaintively; "The lambs were bleating" [syn: bleat,
       blate, blat, baa]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "bleat":
   bark, bawl, bay, beef, bell, bellow, bellyache, bitch, blare, blat,
   blate, blow off, bray, call, caterwaul, crab, cry, fuss,
   give tongue, give voice, howl, low, meow, mew, mewl, miaow, moo,
   neigh, nicker, pule, roar, screak, scream, screech, squall, squawk,
   squeak, squeal, troat, ululate, wail, whicker, whine, whinny,
   yammer, yap, yawl, yawp, yelp, yip, yowl