Riding dirty
For the longest time I thought that expression was referring to something other than drug possession. Driving without a seatbelt. Driving after having crapped your pants. Driving without a license. Driving while in desperate need of a car wash. That sort of thing.
Forza Motorsport 5 provides another definition: treating a previously pristine simulation-quality racing game as a demolition derby. I’m not sure if I should attribute this solely to the Drivatar system, but laps around Forza are more bumper cars than follow-the-leader.