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2.
(n.)It means the endpoint or last source of hard, solid evidence involved in a case or investigation.
This security tape, analyzed by our experts, show that you, Jacob Fry, did indeed rob and murder two victims at the 1st National Bank at Harford and Main.
by Smkngmgc June 13, 2004
 
1.
A piece of evidence that almost is nearly irrefutable. It's origin is from a Sherlock Holme's story and it references how a gun smokes directly after being fired. Therefore if somebody is suspected of shooting a person and they having a still "smoking gun" in their possession, it's evidence that is pretty hard to deny.
1. I know Tom shot Jim, he was still holding a smoking gun when I walked into the room.

2. A: "It's thought that Mary died of an overdose."
B: "Well no one knows for sure yet."
A: "They found heroine and a needle with her DNA on it by the bed"
B: "Oh, I didn't know about that smoking gun"
by Mollination February 02, 2008
 
3.
When a person takes a hit off a joint or a drag from a cigarette, holding the smoke in and sucks a dick before releasing the smoke.
Jen was nervous about doing the smoking gun, she took a long hit before taking Eric's dick into her mouth, taking it all the way in a couple of times, before pulling off and releasing the smoke.
by Jack 'em May 06, 2009
 
4.
when a chick gives a blowjob she smokes a cigarette at the same time. blowing out smoke well giving head.
Bob thought his crotch was on fire but it was mable giving a smoking gun
by Islander86 March 07, 2008
 
5.
Delivering a payload on your partner's chest, then wiping the tip on his or her face.
It was a lousy blowjob, so I capped it off with a smoking gun.
by 'lil stinker March 07, 2004