The act of either jerking off or receiving a traditional hand job at the beach,or a place with comparably sandy conditions. This is in reference to the general sandy and unclean conditions associated with Mexico and select parts of the south western united states. Without this clarification, it is assumed the hand job is without sandy discomfort in its original form.
Bro -"Hey Jim did you get any action with that chick?"
Jim -"Yeah dude, we went to the beach and I got a hand job!"
Bro -"Man, I am really sorry to hear that. Thats called a Mexican hand job."