Having sex with another person vengefully, usually as a way to get back at someone who you may have been sexually involved with. Often involves having sex with a friend of the person who wronged you. Can also involve a proxy, in this case another person has sex with the person who wronged you for the sake of getting the wringers hopes up only to leave them thus satisfying the vengeance.
Guy 1: My girl friend cheated on me man what do I do?
Guy 2: You should hook up with one of her friends and get a "revengelay"
This is something a friend says to you while at school or work when they are having a long day if someone asks you this and you say no you should throw your self into a hole and stay their give this friend lots of head scratch’s and stroke them like a cat