A visible stamp on your hand the morning after a night out drinking.
Many bars that charge a cover will stamp people's hands before they go in so they know who has already paid. When the stamp a person received is still visible the day after, that indicates the person has not showered. Thus they bear the mark of the unclean.
Susie wanted to hook up with Tom in the morning, until she noticed he bore the mark of the unclean.
The creepy uncle that will stick their hands in your ass and marries the type of girl that likes to bounce on booty during the family holiday gatherings.
“Goddammit! I just got a ‘The Uncle Dan’”
“What’d he do?!”
“He tried to wedgie me in the family Christmas dinner!!”