black spleenwort has 1 distinct synonym 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.
spleenwort of Europe and Africa and Asia having pinnate fronds and yielding an astringent
Synonyms, antonyms and the broader and narrower relations for black spleenwort come from Princeton University’s WordNet. Full sources and licences.