WordNet (r) 3.0 (2006):

tummy
    n 1: slang for a paunch [syn: pot, potbelly, bay window,
         corporation, tummy]
    2: an enlarged and muscular saclike organ of the alimentary
       canal; the principal organ of digestion [syn: stomach,
       tummy, tum, breadbasket]

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "tummy":
   abdomen, abomasum, bay window, beerbelly, belly, breadbasket, craw,
   crop, diaphragm, embonpoint, first stomach, gizzard, gullet, gut,
   honeycomb stomach, kishkes, manyplies, maw, midriff, omasum,
   paunch, pot, potbelly, potgut, psalterium, pusgut, rennet bag,
   reticulum, rumen, second stomach, spare tire, stomach, swagbelly,
   third stomach, tum-tum, underbelly, venter, ventripotence