When your labeled by police or doctors as being an endangerment to yourself and others. Once labeled as 51/50, you get taken to a pysch ward for a 72 hour hold to see if your mentally stable.
He threatened to beat up his parents, so they called the cops & they 51/50'd him.
by jdmvero April 5, 2010
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police code meaning crazy and violent. often used as slang meaning the same.
cop: "we have a 51/50 here. im gonna need backup."

person: "that dude's a fucking 51/50. dont mess with him."
by Kennedi Greene August 22, 2007
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Someone who the police, with their poor grasp of psychology, think is a danger to themselves or others. They will generally yell at someone and if they yell back enough, declare them a 51/50. FUCK THE POLICE.
I was in the hospital and some big angry police guy yelled at me and I yelled back, so they gave me the 51/50.
by Downvoting Victim August 21, 2009
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Describes a girl who is both hot and crazy. More specifically, 50% hot and 51% crazy. It doesn't add up. Most times, they are to be avoided. But, sometimes they are acceptable to be around or date.
Mark: dude, check out that girl over there. She's so hot.
James: I wouldn't mess with her. She's a 51/50.

Mark: what are you talking about?
James: she's 50% hot, but 51% crazy. Doesn't add up. I would steer clear.
by Anon Y. Mous 74 December 22, 2011
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Knuckles on my block refer to Bacardi 151 as "that 51/50" Mix half a pint of 51/50 with a 20oz of dole paradise blend. You won't be able to taste it, but you damn sure will feel it.
1. Knuckles is gone off that 51/50 aint tellin what can happen.

2. Owno how I ended up fukkin that crazy bitch, she must have slipped some 51/50 in my orange juice.

3. Dude, I'm to the Liq to get some 51/50 before we hit the club.
by Trinide October 25, 2007
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Murdered out! Black on top of black. So black its hard to see at night.
A all black something i.e. Rims, Car, or Yo Mama! 51/50 Rims!
by Rizzle Tizzle November 17, 2007
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