a term used to wind someone up by not answering there question or just said to just annoy in general.
usually said pitched and with a little cheeky grin and waving of the hand.
-jason : "ah fuck sakes...Will, where have you put my car keys?"
-will: "NI NW"
person bends down to sink to watch their face in the sink and looks up to the mirror to see someone behind them.
- person says "NI NW"