Synonyms of abstruse

Adjective

1. abstruse, deep, recondite, esoteric (vs. exoteric)

usage: difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge; "the professor's lectures were so abstruse that students tended to avoid them"; "a deep metaphysical theory"; "some recondite problem in historiography"

Definition and meaning of abstruse (Dictionary)