FreeVocabulary
Abstruse
/æbˈstruːs/ adjective hardDifficult to understand because it is overly complex, technical, or abstract.
The professor's lecture on quantum field theory was so abstruse that half the class stopped taking notes.
Memory Trick
Picture an idea pushed so far into abstract territory that only a specialist could ever construe it; the 'ab-' prefix suggests the meaning has been pulled away from ordinary understanding.