(adj.) Difficult to understand or comprehend; complex and baffling. Abstract ideas and long calculations are abstruse.
Ab STROOS
incomprehensible; obscure; complex; recondite; esoteric
Sharon struggled to comprehend the abstruse theories that some of her friends came up with during lunchtime discussions.
In a Quote:
"Then he drew himself out, and having satisfied himself upon some abstruse calculation, he carefully stretched the wire across the front of the hencoop and held it in place with his left hand while his right groped behind him for hammer and nail."
From The Idler, Jerome K. Jerome

