conventional has 4 distinct synonyms spread across 3 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. Its 2 recorded opposites are unconventional, nuclear.
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.
following accepted customs and proprieties
“conventional wisdom”
(weapons) using energy for propulsion or destruction that is not nuclear energy
“conventional warfare”
unimaginative and conformist
“conventional bourgeois lives”
rigidly formal or bound by convention
“their ceremonious greetings did not seem heartfelt”
1 of the 7 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for conventional.
Synonyms, antonyms and the broader and narrower relations for conventional come from Princeton University’s WordNet. Full sources and licences.