1. An official photograph taken of someone being brought into police custody, usually characterized by the person wearing a grim or blank expression on their face. The celebrity's unflattering mug shot quickly spread across the Internet overnight following his DUI arrest. I actually managed to make a really goofy face while the cops took my mug shot, which pissed them off to no end.

2. Any portrait or photograph that resembles such a picture. I hate getting my mug shot taken at the DMV for my license—I always look terrible! Wow, nice mug shot! Couldn't smile for the camera, could you?