lewis has 10 distinct synonyms spread across 6 of its 6 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.
United States rock star singer and pianist (born in 1935)
United States athlete who won gold medals at the Olympics for his skill in sprinting and jumping (born in 1961)
United States explorer and soldier who lead led an expedition from St. Louis to the mouth of the Columbia River (1774-1809)
United States labor leader who was president of the United Mine Workers of America from 1920 to 1960 and president of the Congress of Industrial Organizations from 1935 to 1940 (1880-1969)
United States novelist who satirized middle-class America in his novel Main Street (1885-1951)
English critic and novelist; author of theological works and of books for children (1898-1963)
Synonyms, antonyms and the broader and narrower relations for lewis come from Princeton University’s WordNet. Full sources and licences.