na-adjective
Describes a person, attitude, or approach that is intellectual, rational, or cerebral, often contrasted with emotional or practical orientations.
彼は主知的なアプローチで問題を解決した。
He solved the problem with an intellectual approach.
その議論は主知的すぎて、一般の人には難しかった。
The discussion was too intellectual and difficult for ordinary people.
理性的 means 'rational', emphasizing logic and reason; 主知的 leans more toward intellectualism or a cerebral orientation.
Compound of 主 (しゅ, 'main, primary') + 知的 (ちてき, 'intellectual'). The exact historical derivation is uncertain, but the word follows a common pattern for forming adjectival nouns.