can refer to a place where learning is done, usually a shul like area with lots of holy books. Can also mean the after high school study programs that many boys attend in order to learn torah full time and earn a Bachelors in Talmudic Law at the same time. Context would be “ oh he is in the beis medrish now, catching up on Lost with his chavrusah” or “He is a beis medrish guy”