Sticky residue, also know as semen, left above the upper lip of the person who just gave a blow job. The semen dries to give the appearance of a white mustache. Got cum?

when you're hungover as shit after a spending a night drunk as a skunk

A mustache of semen (cum) that is delacately layed on the upper lip of a female, or in a homosexuals case on the upper lip of a man. This can be licked off by any partner and deposited into a sink or swallowed. Make sure there are no STD's while preforming this sexual activity. Best done after oral sex.

After the act of oral sex, on occasion the partner's cum is left behind on the upper lip, under the nose. This can resemble a mustache and commonly confused as a milk mustache.

A mustache of cum after one tries to swallow.

residue from oral sex around your lips.

when a girl gets cum above her lip under her nose, like a mustache