Smudged Lipstick
When a woman gives oral sex to a man after he has pulled his penis out of her vaginia during which she was on her menstrual cycle. Thus giving her what looks like "Smudged Lipstick".
What I did last night, actually. Her period ends up on her face via the man's penis, thus giving her a "Smudged Lipstick". It looks like when a woman had on lipstick buy got "smudged" or "smeared" all over her face.
lipstick smudge
an affair
"I need to get rid of my lipstick smudge"