A person who likes anything and everything that "everyone" likes (trends, etc.) for the sake of being cool. Once that trend ends and everyone stops liking it, they promptly start disliking it and it becomes the worst thing in the world. They also mock the people that continue to follow the "uncool" trends.
Billy: Wrestling's so gay, why do you watch that? I can't stand that crap.
Billy (3 years earlier): Stone Cold rules!