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3.
Also known as a third wheel... when a dating couple or almost dating couple decide to spend sometime together but one of the guys or girl friend is there. Sometimes this turns into Cockblocking.
I was with my GF and my friend who lives next to me was being a third nipple and wouldn't leave us alone
by ROCK!!!!! December 15, 2009
 
1.
A mole often directly between the two real nipples. Completely useless as a nipple.
Carlos has a third nipple!
by truecha January 17, 2006
 
2.
Used in the phrase "Don't take it to the third nipple!"
The "third nipple" is non-existant because it's one too many body parts we need, so it's used to refer to when someone is over reacting to something or is about to say something that's exaggerative (<-is that a word?).
"Oh my GOD!! I'm going to kill you! You lil' sonuvabitch!! Why I ought.."
"Whoa dude, don't take it to the third nipple!"
by SellOutBoy May 13, 2009
 
4.
something completely useless.
I need cancer like I need a third nipple.
by leeroy genkins August 10, 2005