Dirty mug

1: Meaning to be an ugly person, often derived from the expression 'ugly fuck'.

2: Defined as a person who was raised in the country,
also called a 'redneck', 'white trash'.

john: "stop touchin' me ya dirty mug!"

Dirty mug

Licking a waitresses butthole after a “double shift”.

Meaning she has just been freshly DPd by two randoms and you got the clean up

Steve: “Are you hooking up with that waitress tonight?”
Bill: “Yup”
Steve: “ Make sure them dishes are clean. You don’t want her giving you a dirty mug”