Englishabstruse
adjective
he was unable to follow the abstruse arguments put forward:
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;
rare involute, involuted.
▷antonyms clear, obvious.
abstruse Oxford Dictionary of English