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1.
Acronym for "Person of Unknown Origin." Refers to a person whose racial/ethnic background is not immediately obvious. Popularized by radio personality Howard Stern.
"I thought Angelina Jolie was Asian, then I found out her father is white. I guess she's a P.U.O."
by Dorothy May 07, 2005
 
2.
PUO
Pick Up Only, usually used when selling things through a site like Craigslist
Selling three used condoms $500 firm. PUO
by Ralphlikesglue December 26, 2013
 
3.
Soup spelled backwards
Fred:Hey Jimmy, what's soup spelled backwards?"
Jimmy:Well puos of course!
Fred: You're so smart!
by Jim Bob Sherward June 25, 2012