catechu has 3 distinct synonyms spread across 2 of its 2 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.
extract of the heartwood of Acacia catechu used for dyeing and tanning and preserving fishnets and sails; formerly used medicinally
East Indian spiny tree having twice-pinnate leaves and yellow flowers followed by flat pods; source of black catechu
Synonyms, antonyms and the broader and narrower relations for catechu come from Princeton University’s WordNet. Full sources and licences.