pumpkin has 3 distinct synonyms spread across 1 of its 2 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.
a coarse vine widely cultivated for its large pulpy round orange fruit with firm orange skin and numerous seeds; subspecies of Cucurbita pepo include the summer squashes and a few autumn squashes
usually large pulpy deep-yellow round fruit of the squash family maturing in late summer or early autumn
Synonyms, antonyms and the broader and narrower relations for pumpkin come from Princeton University’s WordNet. Full sources and licences.