This is one of those abbreviated slangs that Koreans LOVE to use! Let’s break it down to understand the meaning: 

Put together, it would mean a kind of person who wants attention! In other words, an attention seeker. Of course you can use this as an insult but it is also lighthearted when it is between friends or when the situation calls for it. If you are laughing at your friend who seems to be really really outgoing – like dancing on a table at a bar or something you can be like omg you’re such a 관종 !!! *In the most loving way possible please don’t use this to insult others or make people feel small!!!!!