The beginning of counting down for someone to chug their beer, or drink they must drink. And if the whole thing is sung and they haven't finished their drink then they don't deserve to be at your party.
(The full P.C. phrase: Down in One! , Down in One, Down in One, Down in Two, Down in Two, Down in Two, Down in Three, Down in Three, Down in Three, Down in Four ... You're a Bore, Why are we waiting we could be masterb*ting, Drink MF, Drink MF Drink!)
Drunk Party People: *Playing Kings Cup*
Very Drunk Bro: *Gets stacked* Damn it, I lost.
Everyone else: Down in One!...
Very Drunk Bro: *Finishes by Two*
Me: Well that's what you get for standing to the left of me.
by Investigate311#BirdUp April 19, 2019
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One-downing is simply the opposite of one-upping.

Also known as a "race to the bottom." This tactic is used by everyone from fast food produces, horror movie directors, indeed the President of the United States of America, to shock people by showing them that the bar can still be lowered.
While many fast food producers are scrambling to one-up each with healthy offerings, KFC is one-downing them all the with the double down sandwich.
by SearchFHG June 13, 2018
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Wen you breeze one down, then u r a little legend, it means to have a poo poo!
"breeze one down u little legend, scat judge g unit nigwoar!
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