It was first used in PC games such as CS you console faggot.
See me quick scope two of those terrorist.
A Quick scope was born from the Call Of Duty and Halo franchises. The idea is to pull in your scope and shoot at the moment you see your crosshairs. this can be useful in combat because a skilled player may be able to pull this off and get accurate, one-shot kills. This is normally for show and is not the best way to play unless you want to impress others by making videos or compilations. Machinima.com is a great place to find these montages and skill in Quickscoping.
xXLegi1tSnipeZz x tried to knife me but i Quick Scoped him and got a one shot kill. stupid nooblet.