ONS is an acronym indicating the common dating phenomenon One Night Stand. You can use the acronym ONS to indicate a person with whom you have had said One Night Stand.
You: "Uh-oh, guess who just walked in?"
Me: "Shit. Who?!"
You: "ONS"
Me: "Great... and I thought I'd never have to see him again."
by Roberta Pincer April 11, 2005
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This stands for "One-Night-Stand" and is used by some males to inform thier friends what they think of certain women in the club.
Check her out!! She is definately an ONS I wouldnt mind havin tonite!
by Shinshoryuken January 14, 2006
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Onslaught, a game mode in Unreal Tournament 2004 where players trying to capture nodes to eventually make way to the enemy base and try to destroy the power core.
It takes good team strats to win at ONS.
by CorporationX February 18, 2005
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ONS is an abbreviation for "Over Night Studying", SON can also be used in some occasions. It is an action held by most, if not all, petroleum engineering students. It has been well known through out time, that this habit is to be practiced before major exams, and even quizes. According to new Petroleum engineering students, ONS is a sacred retual, that every -successful to be- engineer should experience!
"Normal student Helal" : Ughh, Got a midterm tomorrow, ONS :D ??

2 years later..

"ADMA executive manager HaLool :3" : SON was worth it alright :3!
by Hallulz November 20, 2010
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An informal code of street fighting, not allowing bystanders to interfere in the fight.
Hey bitch-ass, let's square it up one-on-one in the midldle of the street!
by PGrace August 5, 2003
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1. A game where the only opponents are two people playing against each other.
2. Also know as speedballing; a mixture of cocaine and herion, most often injected.
1. Jack says to Tommy, "Let's play a game of one on one"
2. After getting out of lock-up, I said to myself, "I'm 'bout ready to head downtown and gets me a one on one!!"
by dieselgirl August 7, 2003
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