The ultimate of all n00b insults, it refers to someone who is such a newbie at life in general that you must insult them twice within one word to get your point across.
Side note: it is a palindrome.
Graham: "Are you drinking Boone's Farm wine while maintaining a .25 kill/death ratio again Josh?"
Josh: "I like Boone's Farm, and what is a kill/death ratio?"
Graham: "Wow you're a n00bb00n!!!"