no duff

Meanings

1. Indicating that this is not a drill or training exercise.

1. An incident that is not a drill or training exercise; an emergency. Also end of exercise. Stop drill immediately. As a ‘tap out’ called by during physical training. Sim munitions training in Australian Swat ‘end ex’.

Etymology

From the RAF slang expression "duff gen" meaning bad or fake information; "no duff", by extension means "accurate", also: "stop operations until ordered otherwise". It comes from the term "No Direction Finding" in the British Army in regards to radio/signals procedure. It was used when in training or on exercise to pass a message true in nature but not related to the aims of the exercise. This could be an accident, change of exercise requirements, etc. This means the message to be sent should not be subject to radio direction finding to locate the transmitting station by either the blue or red side. i.e. "Hello zero this is two one alpha, NO DUFF message over". "NO DUFF two one alpha this is zero, roger out to you, hello all stations this is zero stand by for NO DUFF message out, two one alpha send NO DUFF over". "NO DUFF hello zero this is two one alpha, two one bravo has rolled their rover over, over". Normally followed by laughter or expletives from the zero's CP (command post).