rude has 14 distinct synonyms spread across 5 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.
socially incorrect in behavior
“resentment flared at such an unmannered intrusion”
(of persons) lacking in refinement or grace
lacking civility or good manners
“want nothing from you but to get away from your uncivil tongue”
Synonyms, antonyms and the broader and narrower relations for rude come from Princeton University’s WordNet. Full sources and licences.