suppression has 5 distinct synonyms spread across 3 of its 4 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.
the failure to develop some part or organ
the act of withholding or withdrawing some book or writing from publication or circulation
“a suppression of the newspaper”
Synonyms, antonyms and the broader and narrower relations for suppression come from Princeton University’s WordNet. Full sources and licences.
forceful prevention; putting down by power or authority
“the suppression of heresy”
(psychology) the conscious exclusion of unacceptable thoughts or desires