muffburn

A rash or abrasion received on a mans (or womans) tongue, lip, chin, nose, etc... when he/she has given particuarly active oral sex to a girl. Results from continual rubbing on pubic hair, or pubic hair stubble.

guy1: "Dude, what's up with that rash on your lip?"
guy2: "muffburn man-- 2 hours of oral and I got muffburn!"