Grundlemuffin 

The placing of one's fist into one's grundle and letting it bake there for a minute, then removing it and punching another person across the face with it.

Bitch, if you don't shut your mouth, you're gonna get a big ol' grundlemuffin!

Grundlemuffin by Head Chef McC December 21, 2006

crumblemuff 

A crumbly muffin, and/or weird textured vagina.

"That bitch had a crumblemuff like you wouldn't believe."

crumblemuff by crumblemuff1 April 12, 2014