A n00b is a game player with experience in whatever game they are playing, yet still conduct themselves with no respect for anyone else. Typically a n00b scams, irritates or in any other possible way makes life difficult for other plays. Different to a newb who is simply an inexperienced player.
Player 1: "Some n00b just scammed me!"
Player 2: "What is it with those new players anyway!? No respect!"
Player 1: "Not a newb, they're understandable, n00bs just have problems!"