Abstruse: hard to understand, difficult to comprehend.
English is the clearest language I have ever studied. But, perhaps that is because I did not study English formally. English teachers, it seems, like to muddy the clear waters with their abstruse writing. Don’t believe me? Check this out: http://www.ncte.org/journals/ce/issues/v77-4
Abstruse comes from the Latin verb abstrudo, means, I thrust away, I conceal, or I hide. The Latin verb comes from two other Latin words. The preposition ab means away. The verb trudo means, I thrust, push, or shove.
When someone is abstruse, they are deliberately shoving the clear meaning away from you. Perhaps they are doing this because they want tenure.