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.