horsemint 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.
an annual horsemint of central and western United States and northern Mexico
tall erect perennial or annual having lanceolate leaves and heads of purple-spotted creamy flowers; many subspecies grown from eastern to southwestern United States and in Mexico
Synonyms, antonyms and the broader and narrower relations for horsemint come from Princeton University’s WordNet. Full sources and licences.
a coarse Old World wild water mint having long leaves and spikelike clusters of flowers; naturalized in the eastern United States