An individual who, although may be any age, still resembles a twelve year old. This condition is particularly common among the 'tight nackers, no poobs' brigade.
Ha ha, Sturdy got ID'ed, he's a right twelvey!!!
A word used to describe this kid who spends all of his time in my room and almost none with his actual roomate. He also plays poker all the time.
Hi, I'm Twelvey. My middle name's Hani, and I'm from Hackensack.