1. no duff - Noun
2. no duff - Interjection
no duff
(UK, Ireland, Canada, Australia, New Zealand, Singapore, military slang, radio voice procedure) Indicating that this is not a drill or training exercise.
no duff
(UK, Ireland, Canada, Australia, New Zealand, Singapore, military slang, radio voice procedure) 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’.