An insult that hunters, cops, mobs, or paintball players use. It means that you cant hit shit when you shoot kuz your too fucking gay to learn how to aim or your too friggin weak to hold the gun steady, or you have a crappy scope on your gun and cant aim. Everyone whos seen Star Wars knows that Stormtroopers suck ass at shooting kuz hundreds of them missed hitting Luke and then got their asses kicked.
Hunter : What the hell that friggin moose was right in front of you and you MISSED? Damn you shoot like a Stormtrooper
Cop: You didnt hit the convict? dammit now hes escaped from jail. You shoot like a stormtrooper
Mobs: Dammit you were supposed to whack Jimmy. Whassamottayoo? You shoot like a Stormtrooper!
Paintball Player: Dumbass! Missed me! You shoot like a Stormtrooper!