suffocate has 6 distinct synonyms spread across 6 of its 7 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.
deprive of oxygen and prevent from breathing
“Othello smothered Desdemona with a pillow”
impair the respiration of or obstruct the air passage of
“The foul air was slowly suffocating the children”
Synonyms, antonyms and the broader and narrower relations for suffocate come from Princeton University’s WordNet. Full sources and licences.
be asphyxiated; die from lack of oxygen
“The child suffocated under the pillow”
feel uncomfortable for lack of fresh air
“The room was hot and stuffy and we were suffocating”