Mexican heartburn Share definition Flag A hot and firey rash on the keister, caused by eating hot sauce or hot peppers. After eating a delicious meal at El Pollo Borracho, Margaret got a Mexican heartburn. "It was worth it," she said. Mexican heartburn by Cap'n Bullmoose May 3, 2005 0 0 Get merch Get the Mexican heartburn mug. Buy Now — $32.95 See more merch