smack has 25 distinct synonyms spread across 10 of its 12 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 sailing ship (usually rigged like a sloop or cutter) used in fishing and sailing along the coast
press (the lips) together and open (the lips) noisily, as in eating
Synonyms, antonyms and the broader and narrower relations for smack come from Princeton University’s WordNet. Full sources and licences.