This refers to a derogatory word used for an online gamer in, xbox 360 and ps3, in two different games. The word noobtuber is often used while playing call of duty 4 live, when a player uses grenade launcher attachments on all of their weapons in order to get cheap kills. They usually cannot get kills any other way. It also refers to halo 3 or halo 2 live, when a player uses a rocket launcher and/or a missle pod, and repeatedly uses it as it keeps spawning.
call of duty 4 example:
Lvl 52 Prestige: That fcking noobtuber keeps hitting me with the m16 launcher when I'm sniping. Someone call a UAV already so I can kill that biatch!
halo 3 example:
Col. Grade 2: Stop spawning our rocket launcher at our base you freaking n0obtuber. This is why covies suck: noobtube central