Sorry, send me another one. And call me Ab-Z.

And a newbie is actually one who is new at something. But it is used excessively in games like RuneScape and World of Warcraft, and has been used so much, that no one really knows what a newbie is. Here's what happened:
Newbie>>Newb>>Noob
Noob is now a put-down/insulting term for saying "you suck at this, go away, leave me alone". Also, you see people calling people noobs because they make an offer they consider "noobish" because it is so off what the price is.