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2.
dork, loser, clueless idiot
Albert is a total nine-ball.
by Captain Awesome October 27, 2003
 
1.
an unbelievably stupid person
Did you see that nineball? He thought he could hit on that big dude's girlfriend!
by Mr White January 25, 2005
 
3.
Uninformed, often slow, person whose hobbies include talking about things they don't actually know about. Envies and emulates those that do.

Definition comes from billiards. Being "behind the 8-ball" where one has no shot. Hence Nine Ball.
Video Gamer: "I wish I was a soldier in real life. I'd go full-auto all day."

Soldier: "What about the ammo?...fucking Nine Ball"
by goldengirlsblows January 07, 2011