It means Big Man's Penis - do not associate with Wade from GTA 5, as he states at his cousin's house (When Trevor overhears them talking about him) he hasn't a very large penis.
"Ok, how's yours?"
"A bit slow. Too many files for the folders."
"Hmm. Mine has had a lot of action too recently."
"Really? What type of file?"
"The one on yo mamma!"