intellectual has 4 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. Its one recorded opposite is nonintellectual.
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.
appealing to or using the intellect
“satire is an intellectual weapon”
involving intelligence rather than emotions or instinct
“a cerebral approach to the problem”
Synonyms, antonyms and the broader and narrower relations for intellectual come from Princeton University’s WordNet. Full sources and licences.