To fire a gun (military slang from the days of percussion cap and ball firearms before the manufacture of individual cartidges consisting of a metal casing holding a bullet, gunpowder and a primer that fired when struck by a firing pin or hammer.)
We heard some people busting caps a couple of klicks up the trail.
by jeff August 14, 2004
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This is not a new phrase as much of the Rap culture would like us to believe. Instead it is an old phrase to shoot someone. Reference to cap is a word for powder cap used in percussion guns popular in the old west. This phrase is used in the 1969 movie titled "True Grit" with John Wayne, Glen Campbell, Dennis Hopper and Robert Duvall.

Line by Ned Pepper (played by Robert Duvall) "I never busted a cap (bust a cap) on a woman or nobody under sixteen. But I'll do it."

by J Keto March 10, 2008
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Attested in "True Grit" by Charles Portis, 1968, but most likely much older.

The derivation is probably from the percussion "cap," a small metal cylinder open at one end with an amount of shock-sensitive explosive, usually fulminate of mercury, used to set off the powder charge in a muzzle-loading firearm.

The modern derivation, however, is probably from the "cap gun," a toy firearm using paper "caps" containing Armstrong's mixture or a similar substance to provide the small explosions.
"I have never busted a cap (bust a cap) on a woman or anybody much under sixteen years but I will do what I have to do." -- "Lucky" Ned Pepper
by ET Molligee September 21, 2014
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To discharge a handgun, usually a 9mm, in the direction of an enemy or a rival gang.
Im gonna bust a cap in his punk ass
by HeavenlyHost July 4, 2003
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I found this reference to "bust a cap" in a 1951 Gene Autry novel. Gene Autry and the Golden Ladder Gang by W. H. Hutchinson. Whitman 2349
"I guess it is," said Pres as he regretfully fondled the stock of his rifle, "but I surelee hope that somebody gives me a little excuse to bust a cap in their direction."
-- Gene Autry and the Golden Ladder Gang 1951
by Nick Boxtop March 17, 2018
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To discharge a round of ammunition from a firearm, usually a handgun.
"Fuck wit me, and I'll bust a cap in yo ass, biatch!!"
"That fool was disrespectin' a brutha so I had to straight bust a cap in his ass!"
by Street Shakespeare December 5, 2006
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(v.) for police officer to arrest headwear.
Okay Nikegolf cap, you're busted. Tiger ain't wearin' you no more.
by Gumba Gumba May 20, 2004
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