abstruse abstruse /əbˈstruːs/

adjective

1. Difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge  ( abstruse , deep , recondite )
   difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge
    The professor's lectures were so abstruse that students tended to avoid them
   the professor's lectures were so abstruse that students tended to avoid them
    A deep metaphysical theory
   a deep metaphysical theory
    Some recondite problem in historiography
   some recondite problem in historiography