regurgitate has 15 distinct synonyms spread across 2 of its 4 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.
pour or rush back
“The blood regurgitates into the heart ventricle”
feed through the beak by regurgitating previously swallowed food
“many birds feed their young by regurgitating what they have swallowed and carried to the nest”
Synonyms, antonyms and the broader and narrower relations for regurgitate come from Princeton University’s WordNet. Full sources and licences.