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2.
when you see a girl and shes definately not hot
Guy 1: hey, you think that bitch is hot over there?

Guy 2: WTF, DEFNOOOOO!!!!!!!!
by masterswager July 05, 2009
 
1.
The opposite to Defo
It means definately not.
Person 1: Do ya wanna go into Town?
Person 2: Defno! It's too early.!
by Lloyd W.P February 17, 2008