The act of urinating inside the vagina of a woman during sexual intercourse.
Chad and RayRay are in the middle of fucking...

Chad: "Do you want me to pee inside you?"

RayRay: "No thankyou. I'm not interested in recieving a Mexican Fountain from you. Tell your dugan to hold it."
by Dr. Humpsalot December 14, 2004
Get the Mexican Fountain mug.
Initial steady stream of shit disbursed through the anus ( usually accompanying sever anal burning) whilst on the toilet after a hefty meal of Mexican food.
"I was so sick after I ate five tacos at that Mexican restaurant, talk about a Mexican Ass Fountain!
Get the Mexican Ass Fountain mug.