1. An injury, which the afflicted party does not recall receiving, sustained during a night of drinking.
2. A boo boo you discover the next morning because of something stupid you did the night before.
Based on the song "Party Tattoos" from Ali Spagnola's Power Hour Drinking game
I have so many party tattoos from last night I had to wear a turtleneck in July to cover them. . . also a leg brace.