When you disguise your insult in a joke. Usually done when two parties are mad at each other yet insist on appearing unaffected and cool.
Also commonly used when a person cannot openly insult someone they consider a douche (eg: their boss) and use humor as a way to truly express themselves.
John: What, you painted over this wall with a dead cat?
Sam: Nope. But I would sure love to re-do it with your face! HAHAHA *leaves*
Mark: Why're you laughing dude? He just jokesulted you!