acronym which stands for "Back Fat Fuckin'". Achieved by pushing together two rolls of fat on some fat slut's back and pumping away. A good technique when the rotund cum-dumpster you're rogering has a hatchet wound so loose that it's like throwing a hot dog through a hallway.
You'll get that new aggressive full-blown AIDS if you bone that slutty keg-on-legs.
That's okay, I just plan on doing some BFF'n.