When a female is so ugly that you have to put a bag over her head to have sex.
A vagina is often termed a muffin.
She is so ugly, I can't get with her without a bag. She's a bag a muffin!

Randy's new girlfriend's face is so messed up, she is a bag a muffin.
by cloudowner July 9, 2012
Get the bag a muffin mug.