The priceless facial expression and body movement accompanied by an innocent retail shopper before they exit a store with their paid merchandise, only to be rudely and obnoxiously stopped by the store's alarm which probably only sounded because they had half paper clip in their back pants pocket. Also known as the O-Shit Face.
Sally was just leaving the store when she triggered the store's alarm. She immediately dropped her bags and the baby, mouthing "Oh shit". She also pee'd a little bit.
The clerks along with every customer in the store laughed at her as she slowly turned around, revealing her O-Shit Face.