A sarcastic expression used to describe something that is not fun or unappealing.
The expression fun wow was used in TV and radio advertisements in the late 70's - 80's by a small amusement park in Grand Island, NY that was inferior to many others of its time. People in the Western NY area began using the expression sarcastically to describe anything that wasn't fun.
Person # 1: "Do you want to go to Matt's party Saturday night?"
Person # 2: "Can't. I have to stay home and babysit my younger sister."
Person # 1: "Fun wow"