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."
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"