when a person (or animal) is eating out your asshole and you excrete feces into their mouth.
Cam and his grandpa both gave cam's grandma a mexican mud pie
by Bobby, Bobby Smo November 05, 2006
1 more definition
while a male is fucking a female doggy style he shits in his hand and proceeds to slap her in the face with it.
My girlfriend wanted to have sex with me after fajita night...i gave her a Mexican Mud Pie
by Luke and Matt from Texas June 22, 2008