Translation: The amount of kills versus the amount of times you've been killed.
Proper Usage: "The head of the team told me that in order to join, I'd have to get my kill ratio up."

Just as physical sports fans are obsessed with statistics, so are hardcore first person shooter fans. One of the most important stats FPS enthusiasts monitor is their kill ratio. It's what puts the truly skilled above the lucky. If you've racked up a mess of bullet-riddled corpses but you've been bodied more than times than you've killed, you get no glory. It's those controller maniacs with a low amount of deaths and an awesome trigger finger who are the celebrated gunslingers.