Originally a term used in the card game blackjack, where a player doubles their original bet in exchange for exactly one additional card; most useful when the remaining deck is offering extremely favorable odds of making a total of twenty-one.

The term is increasingly used as a media euphemism when political figures tell bald-faced lies and when confronted with contradictory statements, the politician not only fails to retract their claims but instead expresses an increased certainty in their truth.
The political candidate claimed that 99% of the violent crimes committed in the United States were perpetrated by Canadians. When challenged with data indicating that in fact less that 0.1 percent of crimes are committed by Canadians, the candidate opted to double down, claiming that the data was incorrect. Further, the candidate pledged to, if elected, expel all US citizens with Canadian ancestry from the country.
by Sonicoed June 11, 2017
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to engage in risky behavior, especially when one is already in a dangerous situation.

This figurative usage as appearing in the Oxford English Dictionary is a meaningful explanation of “double down” other than the ubiquitous “to double the wager in exchange for only one additional card in Blackjack gambit” in every online dictionary.
Don’t try to double down the exposures of your retirement money in aggressive investments

It is the time to double down on the commitment of solar energy, rather than to scale back

HP is going to double down on Palm’s webOS
by vanderpol August 4, 2010
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1. Having sex with more then one person at once, most usually a girl taking on two guys and even more specifically alternating between blowing one and the other.

2. In blackjack, to double your current bet at your turn, in return for which you get one more card and then no more. In what situations this is allowed and/or advicable varies somewhat depending on the casino, but if no card counting is done, it's usually a good move on all hands totaling 11 and some totaling 10.
Hey Sue, heard you doubled down last night.

11 to the dealers 6? Double down, no question.
by Patrik Lundin October 6, 2004
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A sandwich that a company markets hardcore to get people excited for, but it doesnt live up to the hype.
Dude I heard some much buildup for the double down but when I tried it was just run of the mill.
by steinhammered April 15, 2010
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The act of performing oral sex to both the genitalia (m/f) and anus.
"I would totally double down on Bjork."
by austinfromsobe/temple October 6, 2008
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v. Upon completion of defecation, standing up and wiping, a sudden and overwhelming urge occurs, compelling the person to immediately sit down and defecate once again.
Just as Fred felt as though he had stopped shitting like a demon; he got up and wiped himself clean. Then all of a sudden a sharp pain in his lower abdomen forced him to double down on the toilet and shit once again.
by scabbrain May 17, 2010
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when a girl is tossing you off and takes two downstrokes without an upstroke in between, often resulting in extreme pain and in worse case scenario a snapped banj!
cindy double downed me last night and my banj hasn't stopped bleeding since.
by pd1b March 8, 2005
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