Someone in a multiplayer video game who waits for someone to weaken their enemy and kills them last second so instead of the person who did all the work getting credit the the person who stole gets it.
Person 1: WOW, that's so gay!
Person B: What happened?
Person 1: This noob just stole my kill!
Person B: I fuckin hate Kill Stealers!
Referring to any person who takes the last shot on an enemy character and only the last shot and getting the kill. can be used for any game. Quite prolific on Halo and COD.
holy shit ive been shooting this guy for ages he must be close to dieing O WHAT THE FUCK HOW DID I NOT GET THAT, YOU FUCKING KILL STEALER.