Someone who transports goods or money between to people in a criminal activity. For example, a thug that comes around to collect extortion money and then brings it to a more senior gang member. Another example would be a lawyer that collects money to bribe a judge.
It's a game. When you burp, you or your friends say "baganga". Then you have to put your thumb to your forehead and wiggle your fingers, pointed upward. If you don't, you'll get smacked on the forehead.