public discussion has 1 distinct synonym spread across 1 of its 1 sense. 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.
free and open discussion of (or debate on) some question of public interest
“such a proposal deserves thorough public discussion”
Synonyms, antonyms and the broader and narrower relations for public discussion come from Princeton University’s WordNet. Full sources and licences.