The sound made in bullet-time (super slow motion) when multiple shots are fired from a gun. The noise is created when the bullet breaks the sound barrier, and the air disruption alone creates sound. Intended to mean that you have a big ass gun, and you intended to shoot the hell out of it, at someone. Legend has it that when someone has enough hate towards their enemy, the bullets themselves take on a life of their own. Instead of just blowing by, they hiss at the victim, and it is said that so many bullets fly at once, that if you hear the tsu tsu, only a miracle can keep you alive.
Eat shit dude otherwise you can feel the wrath of the tsu tsu.