To quote from the American Pit Bull Terrier FAQ:
"This breed of dog, commonly referred to as the pit bull, is largely misunderstood and misrepresented by the public today."
As are the people represented by PITBuLL.
Etymology: A bunch of us in Ann Arbor, Michigan were sitting around talking about which group to march with during the Pride March, and the discussion turned to how difficult it is to decide, because typically one has many different allegiances. So I idly began making a list of all the more marginalized groups within the queer movement, and someone else (I believe it was Robin, now of ISNA), burst out, "Pitbull!!" and the concept was born. We don't actually meet as a group or anything like that, we just sometimes find it a useful concept and label.