when another person swipes their hand under your chin, therefore embarrasing you which makes you want to retaliate. If one gets a sort of sauce (ex. ranch dressing, bbq sauce, ketchup) and swipes it under your chin, you just got pwned.
Enzo stuck his hand in the bbq sauce, went over to John and chin slapped him.
John was so embarrassed he didn't come to school for 2 days.