na-adjective
Describes a person, attitude, or approach that is intellectual, rational, or cerebral, often with a nuance of being cool-headed or analytical.
彼女はとても知性的な人だ。
She is a very intellectual person.
知性的な好奇心を持ち続けたい。
I want to keep having intellectual curiosity.
Formed from 知性 (intellect) + 的 (-like, -al), a standard pattern for creating adjectival nouns.