To the Longboarding community including a wide range of longboarders such as the hippie longboarder, to biff is to lose control of your longboard and fall off causing physical damage to one's self. Biff or 'Biffing' also relates to eating the pavement where one who falls off their longboard hits the ground face first, usually hitting their mouth on a concrete or paved surface (not to be confused with curb stomping).
by JohnnytheFLASH May 03, 2010