buckeye has 4 distinct synonyms spread across 3 of its 3 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.
tree having palmate leaves and large clusters of white to red flowers followed by brown shiny inedible seeds
Synonyms, antonyms and the broader and narrower relations for buckeye come from Princeton University’s WordNet. Full sources and licences.