Leadfoot Clothesline occurs when the driver of a vehicle has to break suddenly at a high to moderate speed. Concerned for the safety of the passenger riding shotgun the driver thinks that in the event the seatbelt fails, or you are not wearing one. They believe they will be able to prevent you from hitting your face off the dashboard or being ejected from the car entirely nulling the laws of motion and momentum, using only but one fully extended right arm. This will always result in a back hand to the chest, neck or face and an immediate apology.
"I guess you didn't see that car pull out, thanks for trying to save me with the leadfoot clothesline but now my chest hurts."