They don't even need a definition. They're like illuminati. Say something about them and they'll come after you with a fucking knife. They love five singing idiots, so you don't even have to point out they're stupid. They waste their lives using the JHLEGYDH language, crying over shirtless pictures of their husbands, and losing ovaries. Directioners have feels that you can't even imagine. These girls, or guys, would use every last penny they own to buy a doorknob that Harry touched. They struggle and cry over simple things such as deciding who's name to write last. Oh, and don't EVER confuse a directioner for a directionator. EVER. Good bye peasant.
If you still wear stripes and think it's funny, you aren't a directioner.