Batfacing

Batfacing is a facial expression of someone who finds something so funny and/or outrageous that they can’t stop laughing. In some cases the person may not even be able to laugh audibly and results in a silent shrugging of the shoulders and accompanied by tears welling up in the eyes.

Joe: “Did you hear the joke David said during class?”
John: “Yeah man, it was so good I was batfacing.”