The Collaborative International Dictionary of English v.0.48:

Bellyache \Bel"ly*ache`\, n.
   Pain in the bowels; colic.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bellyache \Bel"ly*ache`\, v. i.
   to complain, especially in a whining or grumbling manner; to
   gripe.

   Syn: gripe, whine, complain, moan, snivel, grumble, squawk.
        [PJC + WordNet 1.5]

WordNet (r) 3.0 (2006):

bellyache
    n 1: an ache localized in the stomach or abdominal region [syn:
         stomachache, stomach ache, bellyache, gastralgia]
    v 1: complain; "What was he hollering about?" [syn: gripe,
         bitch, grouse, crab, beef, squawk, bellyache,
         holler]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "bellyache":
   ache, aching, air a grievance, angina, backache, beef, beefing,
   bellyaching, bitch, bitching, cephalalgia, clamor, colic,
   collywobbles, complain, complaining, complaint, crab, croak,
   destructive criticism, dissent, earache, faultfinding, fret,
   fret and fume, fuss, gnawing, grievance, gripe, gripes, griping,
   groan, groaning, grouch, grouse, grousing, growl, grumble,
   grumbling, grunt, gut-ache, headache, heartburn, hemicrania,
   holler, howl, kick, kicking, lodge a complaint, megrim, migraine,
   murmur, murmuring, mutter, odontalgia, otalgia, peeve, peevishness,
   pet peeve, petulance, protest, pyrosis, querulousness,
   raise a howl, register a complaint, scolding, sick headache,
   sniping, splitting headache, squawk, squawking, stomachache,
   take on, throbbing pain, toothache, whining, yap, yapping, yelp