Easily recognized, as most servers will fill up with players with the lowest rank / level.
How is that kid only a level 17?!?! Oh, wait...christmas noob.
Gamer 2: Fucking right! All those Christmas noobs will be playing. I can't wait to pwn me some Christmas noobs!
Gamer 1: You know it!
MW3 Player 2: "Oh, don't mind him, he's a Christmas Noob."