No duff means: 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. It is military jargon and mostly appears in service contexts, war fiction, or among veterans and their families. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour.
no duff
(UK, Ireland, Canada, AU, NZ, Singapore, military slang, radio voice procedure) An incident that is not a drill or training exercise; an emergency.
Definitions
UK
#1·Apr 27, 2026UK
(UK, Ireland, Canada, AU, NZ, 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’.
“Get him in here, and radio a ‘no duff’ [casualty] to HQ.”
Origin: 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. Origin information sourced from Wiktionary contributors (CC BY-SA 4.0).
For parents
No duff means: 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. It is military jargon and mostly appears in service contexts, war fiction, or among veterans and their families. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour.
For ESL learners
no duff means: 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. Register: informal, military jargon. Suitable only for casual conversation, chat and social media. Do not use in business, academic or news writing. A common learner mistake is using the word in a register it does not fit, or assuming a single global meaning; native speakers immediately notice when slang appears in formal contexts, so always check the surrounding register before producing it yourself.
Cluster: approval
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Why is this section here?
Slang is read by different audiences for very different reasons. The For parents view re-explains the term in plain, non-judgemental language so a caregiver can understand what their child means without needing the surrounding subculture. The For English learners view focuses on register (when it's safe to use), formal alternatives, and common mistakes — what a textbook won't teach you.
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