cudweed has 7 distinct synonyms spread across 2 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.
any of numerous plants of the genus Gnaphalium having flowers that can be dried without loss of form or color
any plant of the genus Filago having capitate clusters of small woolly flower heads
perennial cottony-white herb of southwestern United States
Synonyms, antonyms and the broader and narrower relations for cudweed come from Princeton University’s WordNet. Full sources and licences.