The act of shifting a motor vehicle into reverse gear while on a highway in order to back up and to get onto an exit ramp one has already passed. This term comes from the New York Metro area, where Asians and Caucasians have conducted a nonscientific study by looking to see what the person taking this action looked like only to find that they are black at least 90% of the time.
> "Look at this fucking guy blacking up on the highway..."