WordNet (r) 3.0 (2006):

holler
    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]
    2: a small valley between mountains; "he built himself a cabin
       in a hollow high up in the Appalachians" [syn: hollow,
       holler]
    v 1: shout out; "He hollered out to surrender our weapons" [syn:
         holler, holler out]
    2: utter a sudden loud cry; "she cried with pain when the doctor
       inserted the needle"; "I yelled to her from the window but
       she couldn't hear me" [syn: shout, shout out, cry,
       call, yell, scream, holler, hollo, squall]
    3: complain; "What was he hollering about?" [syn: gripe,
       bitch, grouse, crab, beef, squawk, bellyache,
       holler]

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "holler":
   air a grievance, bark, battle cry, bawl, beef, beefing, bellow,
   bellyache, bellyaching, bitch, bitching, boggle, boycott, call,
   call in question, caterwaul, challenge, cheer, clamor, complain,
   complaining, complaint, crab, croak, cry, cry out against,
   demonstrate, demonstrate against, demur, destructive criticism,
   dispute, dissent, enter a protest, expostulate, faultfinding, fret,
   fret and fume, fuss, grievance, gripe, griping, groan, groaning,
   grouch, grouse, grousing, growl, grumble, grumbling, grunt, hail,
   halloo, hollo, hoot, howl, hurrah, kick, kicking,
   lodge a complaint, march, murmur, murmuring, mutter, object, peeve,
   peevishness, pet peeve, petulance, picket, press objections,
   protest, querulousness, raise a howl, rally, rallying cry,
   register a complaint, remonstrate, roar, scolding, scream, screech,
   scruple, shout, shriek, sit in, sniping, squall, squawk, squawking,
   squeal, state a grievance, strike, take on, teach in, vociferate,
   war cry, war whoop, whining, whoop, yammer, yap, yapping, yawl,
   yawp, yell, yell bloody murder, yelp, yo-ho, yowl