suck has 20 distinct synonyms spread across 6 of its 8 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.
draw into the mouth by creating a practical vacuum in the mouth
“suck the poison from the place where the snake bit”
draw something in by or as if by a vacuum
“Mud was sucking at her feet”
provide sexual gratification through oral stimulation
Synonyms, antonyms and the broader and narrower relations for suck come from Princeton University’s WordNet. Full sources and licences.