look up any word, like fap:
 
1.
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!"
by yoshi May 05, 2004
 
2.
little red bumps on a man's lower abdomen caused from being ridden by his woman after she has recently shaved down there.
I was so excited my girlfriend shaved her muff, but the next day I had muff burn from the little hairs trying to grow back.
by Cap'n Positive January 07, 2012