The action of jumping and/or running over the top of a car or other vehicle while the vehicle is in reasonable movement. (at least 10 mph)
To successfully Bust an O'Conner, you must land it. If you don't land an O'Conner it's called Bustin' Your Lip. (Not correlated with Bustin' A Nut)
Safe Seth the Safety Bear displays an example of Bustin' O'Conners:
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Displayed in the video, the man attempting to Bust the O'Conner, however he Busts his Lip.