What did Gen. McAuliffe mean when he said NUTS to the germans?

Question

Can someone tell me what does NUTS means in that "sentence" ?

Answer 1

It was a WWII era American slang to convey not merely refusal to cooperate, but defiance as well.

It was the second best such refusal of the War.  The best was during Operation Market Garden, in Arnhem.  The British 1st Airborne was surrounded and cut off with no hope of rescue.  A German messenger was sent over to convey that the German commander wished to discuss the terms of surrender.  The British response was "We haven't the facility to take you all, sorry."

Answer 2

It was his way of saying, "Go to h**l".

The Germans were trying to convince the Allies to surrender.