difficult to understand; obscure.
“an abstruse philosophical inquiry”
synonyms: obscure, arcane, esoteric, little known, recherché, rarefied, recondite, difficult, hard, puzzling, perplexing, enigmatic, inscrutable, cryptic, Delphic, complex, complicated, involved, over/above one’s head, incomprehensible, unfathomable, impenetrable, mysterious; More
“he was unable to follow the abstruse arguments put forward”
antonyms: clear, obvious