tumbleweed has 8 distinct synonyms spread across 3 of its 4 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 plant that breaks away from its roots in autumn and is driven by the wind as a light rolling mass
prickly bushy Eurasian plant; a troublesome weed in central and western United States
bushy annual weed of central North America having greenish flowers and winged seeds
bushy plant of western United States
Synonyms, antonyms and the broader and narrower relations for tumbleweed come from Princeton University’s WordNet. Full sources and licences.