da biff: Simple, bogan form of "The Biff." Often extended into a very long sylable, to be uttered as a extended groan, to point out the various uncultured tendencies of those who cry out, "Bring back the biff."
Derogatory, comes from the name of a British skip company, a 'biffa' is a fat person.
Describing something as biffing is like describing something as huge.