A noob (a.k.a. nOOb, n00b, nOOber) is a pejorative term for a player at a game (usually a MMORPG) who is relatively new (in the literal sense) or whose skills are inadequate (metaphorically). Ironically, if one uses the word "nOOb", that means they are quite addicted and don't have a life.
Random player: Gt th hel out, u nOOB!!1!!