stomach has 17 distinct synonyms spread across 3 of its 6 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
an enlarged and muscular saclike organ of the alimentary canal; the principal organ of digestion
the region of the body of a vertebrate between the thorax and the pelvis
an inclination or liking for things involving conflict or difficulty or unpleasantness
“he had no stomach for a fight”
an appetite for food
“exercise gave him a good stomach for dinner”
bear to eat
“He cannot stomach raw fish”
Synonyms, antonyms and the broader and narrower relations for stomach come from Princeton University’s WordNet. Full sources and licences.