Backmuffin 

sarcastically saying that someone usually a male has a "nice ass" but has a flat ass but its still pretty nice and soft

mmmm you are a backmuffin

Backmuffin by buttmuffin100000 June 10, 2011

yackmuffin

when you throwup in and around a girls muff and lick it out

dude1: dude i had myself a yackmuffin the other nite
dude2: sheckler is gay

yackmuffin by jimi stone April 3, 2008