When, In an FPS game (or, even better if its IRL), you try to be an ubeR 1337 h@X0r n00b and go for a headshot, but miss and get a neckshot,which means you fail. (if the target is standing still, it is an epic fail.)
FPSguy1234: "hehe n00bs..."*sneaks up right behind enemy soldier with sniper rifle and takes shot at point blank range, and completley fails at headshotting, and thus hits the neck*

"Boom Neckshot!"

enemy soldier: "lol u fail n00b"
by -abyssion- April 3, 2010
Get the Boom Neckshot! mug.