Contrary to its recent misuse as a euphemism for audacity or courage, to have "brass balls" actually means to drive a hard bargain and to refuse to sell for less than what you ask for.

The term dates back to the days when pawn shop brokers would traditionally hang three brass balls outside their shop doors to indicate their services.
You mean to tell me that this guitar is only worth $15? You've got some real brass balls on you!
by Down10 March 7, 2007
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A pair of metallic spheres, each approximately 2 inches in diameter, connected by a string or chain and meant to represent the male testes. Used as a motivational tool by Alec Baldwin in the 1992 film version of David Mamet's Glengarry Glen Ross.
It takes brass balls to sell real estate.
by BMG January 16, 2003
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'Brass balls' are what Santa's elves need, when they complete their work for Christmas. Reference comes from 2005 Saturday Night Live skit, featuring Alec Baldwin.

Alec Baldwin waved those brass balls in front of Santa's elves - was that a call to glory, or just showing off?
by Rat Genesis March 19, 2006
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Refering to ultimate manliness, courage, or endurance that a man may possess.
Long distance runners must have brass balls to endure thier intence training.
by Most Fruitful Dar April 28, 2009
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