In the gaming world, a "b00ster","b00stor",or "b00ztorz" is a player with a high rank to begin with, who creates another account for personal gain. The way this works is, the player will create another account that begins at a low rank, and because they are good at the specific game they are playing, they earn XP (experience points) faster, and get boosted to a higher level faster.
Usually in online gaming, you are matched up with people the same rank as you. The b00stor will go on his low rank account, and start pwning the noobs he gets matched up with to earn XP, which makes him level up faster than others.
A Five Star General creates an alternative account (b00ster account), and gets matched up with a bunch of Privates. He then pwns the privates, and earns XP, and his player levels up (or boosts his level).