A twelvie is a 12yo girl or boy that acts way older than they actually are, and acts ridiculously annoying. They also try to be cool, but epicly fail.

A kid ages 12-15 who acts and thinks they are older than they actually are.

Someone between the ages of 12-15 and is really annoying

The Police. Any law enforcement agent. See also "12", "PO-PO", and "ONE-TIME."

Mainly used to describe young (12-15) rich white boys and girls who use their parents money to buy marijuana. Then they proceed to post about it all over social media, eventually proceeding to them being caught by their rich parents. Then the cycle starts all over again.

Year 12 students (of age ) who think they're top shit because they're living it up (boozed up and clubbing in town

Trust me, this comes from experience 😂. I get called it all the time because I’m a total twelvie. I wear makeup even to school, I’m always swearing and screaming and I am always wearing crop tops and chokers on weekends. It basically means someone who is 12 and acts older than they should.