One who shows interest in a person for their superfluous intelligence. Now, that alone may sound positive. This, however, is not the case as brain diggers would only like to use the brainpower for their own selfish needs.
1.Girl 1: You are such a brain digger.
Girl 2: What? Why!?
Girl 1: You only make friends with the smart people so you don't have to think of stuff on your own.
Girl 2: I'm sorry!