0 and X
A phrase used when somebody has died and gotten zero kills throughout the game. This usually applies to online shooting games like Call of Duty or Rainbow Six: Siege. The "X" represents the amount of times the player has died, for example if they died 5 times, it would be 0 and 5. The number replaces the X, while the X acts as a placeholder.
Derek: Bro you're legit garbage at the game.

Jason: Shut the hell up, you're 0 and X shitter. Get a kill before you try to talk shit.