Synonyms for (adjective) abstruse

Synonyms: abstruse, recondite, deep

Definition: difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge

Usage: the professor's lectures were so abstruse that students tended to avoid them; a deep metaphysical theory; some recondite problem in historiography

Similar words: esoteric

Definition: confined to and understandable by only an enlightened inner circle

Usage: a compilation of esoteric philosophical theories