some sort of temporary tattoo given while asleep. Usually given by the dumbass friend who was bored and had either a Sharpie or a black ink pen. The face is usually the best place to lay some awesome Sleep Ink.
Carlos: Dude, why do you have a vagina drawn on your chin???
Ceasar: lmao!!! Like, that took an hour to draw!!!
Ronnie: *Strangles Ceasar to death*
Carlos: Careful, Dude. you don't wanna mess up your Sleep Ink!!!