1) Greek people (especially teenagers) use it in order to make someone else feel like he is a stupid person and he is reall lonelly.
2) They also use it in order to make someone feel a starter, most known as a noob, newb, n00b etc.
3) It is a way to communicate with other people. If you don't want to say ''hey malaka''(= hey ass) in Greek, you can say ''hey Exior''. (Mostly used by students during School. If they say malakas, they teachers will understand it, but if they say exior, they hae no clue of what it is all about.
2)Oh my god, Manolis is the worst exior i have ever met. He has been practising Karate for 2 years and he doesn't even know how to give a punch to the opponent!
3) -Hey Exior, whats up? - Dude, the Ancient Greek teacher put us study 3 pages with nouns and pro-nouns.