actaea rubra has 4 distinct synonyms spread across 1 of its 1 sense. 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.
North American perennial herb with alternately compound leaves and racemes of small white flowers followed by bright red oval poisonous berries
Synonyms, antonyms and the broader and narrower relations for actaea rubra come from Princeton University’s WordNet. Full sources and licences.