The best-kept secret in the sexual world. When a man sprinkles taco seasoning on his dong and fucks her up the ass so fast that the girl's anus begins to smoke, he can say he gave her a mexican smokestack. The friction generated with the taco seasoning causes the burning to actually smell like mexican food. I love it.
"...that was disgusting!"
"Not as disgusting as Michael giving Maggie a mexican smokestack."