When someone with a mustache (male or female), administers oral sex on a female and lets the vaginal fluids crustify onto the mustache.
by The PGP January 18, 2010

Matt:"Dude, I totally ate a crusty muffin last night!"
Kevin:"Really, was it warm, fresh and tasty? Did you spell out the alphabet??"
Kevin:"Really, was it warm, fresh and tasty? Did you spell out the alphabet??"
by Matt (Crusty Muffin Man) June 02, 2007

When the anal cavity is penetrated with such viciousness that it pulls the rectal out; creating a hemroid that resembles the top of a muffin that is bloody and crusty with semen.
by Jamoocaba February 04, 2010

A crusty muffin is a slang term for a very unclean vagina. Typically with flakes of crusty skin, dried semen, dried discharge, or any other patina of std origin.
by victim of s.d.s.r December 12, 2023
