BDFU Share definition Flag Bac Da Fuc Up. Acronym for the term derived from the Onyx album of the same name. Pussass nigga! Best BDFU! Move back, muthafuggaz, the Onyx is here! Bacdafucup, just bacdafucup. BDFU by Phat Pat March 24, 2006 0 0 Get merch