Someone who is constantly on the internet on one or more of the following websites.
If you're doing nothing, you're on one of these websites.
Friend: Whatcha doin?
Me: On tumblr looking at pictures of Youtubers... Oh and tweeting stuff on twitter... AND, and watching Cry play The Last Of Us on Youtube
Friend: Internet Addict much?
Me: YOU DON'T UNDERSTAND it's too many feels!