chunky chalupa

When a man (or another female) eats a large amount of Mexican food, creating extremely greasy diarrhea. They then shit into and onto a vagina, and continue to use the mud-butt grease as lube. It is called a chunky chalupa because diarrhea is known to have small chunks in it.

Girl 1: "I heard Jeff gave you a chunky chalupa, he musta had a bad case of mud butt.
Girl 2: "He didn't, that's just bull shit!"
Girl 1: "Heard he slurped the chunks out"