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1.
"Not telling you" is an expression you use when you want to piss off people by not telling them something the want to know.
Guy1: I had sex last night, want to know who I had sex with?
Guy2: Who? Who?
Guy1: Not telling you.
Guy2: Oh fu...
Guy1: Don't curse, mister!
by Fotus9 January 10, 2009