The throbbing, oversized lips of a STD infected mouth. Usually received from putting your mouth on a muffin dick or a vagina muffin (see my definitions for these). They hurt like a bitch and people won't understand what the fuck you're saying. Muffinlips cannot be cured.
"Hey dude I licked my girls vadge and now my lips hurt" "I can't understand you but fuck I think you have muffinlips."