clay has 9 distinct synonyms spread across 4 of its 5 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.
a very fine-grained soil that is plastic when moist but hard when fired
United States general who commanded United States forces in Europe from 1945 to 1949 and who oversaw the Berlin airlift (1897-1978)
United States politician responsible for the Missouri Compromise between free and slave states (1777-1852)
Synonyms, antonyms and the broader and narrower relations for clay come from Princeton University’s WordNet. Full sources and licences.