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1.
Mountain fucking Dew.
Yo bro, pass me that yak piss.
by iamredi July 19, 2012
 
2.
An alcoholic beverage that is either cheap or weak, or both, notable by a pale yellow colour, and an unrefined taste. The term originates from the 2002 film The Scorpion King, where one of the characters mentions it.
Arpid: He's been drinking that yak piss for hours.
by Sharkie August 04, 2008