The gun is basically you do the gun symbol with you hand and the two fingers go into the hole of the female and your finger basically flicks their bean. Simple.
A person of whom preforms so well at their chosen activity and makes such an impact and with such apparent little effort, on their part, that it warrants a comparison to that of the a gun in a sword fight.
Criminal : I need a barrister to get me off this charge.
Mate: Have you heard of that guy in Canberra, they call him "the gun."
Criminal : Why do they call him "the gun?"
Mate: Because he gets everyone off
This is when you are eating out a womans vagina untill her fluids fill up your mouth. then without swallowing the secretion, spit it all out into her rectum. then begin having anal sex with her.