The Collaborative International Dictionary of English v.0.48:

Ululate \Ul"u*late\, v. i. [imp. & p. p. Ululated; p. pr. &
   vb. n. Ululating.] [L. ululatus, p. p. of ululare to howl,
   yell, shriek.]
   To howl, as a dog or a wolf; to wail; as, ululating jackals.
   --Sir T. Herbert.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ululate
    v 1: emit long loud cries; "wail in self-pity"; "howl with
         sorrow" [syn: howl, ululate, wail, roar, yawl,
         yaup]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "ululate":
   bark, bawl, bay, bell, bellow, bewail, blare, blat, blate, bleat,
   bray, call, caterwaul, creak, cry, cry out, give tongue,
   give voice, groan, howl, keen, low, make an outcry, meow, mew,
   mewl, miaow, moan, moo, neigh, nicker, pipe, pule, quest, roar,
   screak, scream, screech, shriek, shrill, skirl, skreigh, squall,
   squawk, squeak, squeal, tirade, troat, wail, whicker, whine,
   whinny, whistle, wrawl, yammer, yap, yawl, yawp, yell, yelp, yip,
   yowl