A dud is an ammunition round or explosive that fails to fire or detonate, respectively, on time or on command. Poorly designed devices (for example, improvised explosive devices (IEDs)), shoddy worksmanship at the munitions factory, over-complicated fuzes, and small devices, have higher chances of being duds.^{[citation needed]} During the Continuation War 1941-1944, Finns estimated up to 20% to 30% of all Soviet shells would be duds.

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Dud shell lodged in a tree, Argonne Forest, First World War

British dud during World War I

Duds are still dangerous, and can explode if handled. They must be deactivated and disposed of carefully. In war-torn areas, many curious children have been injured or killed from tampering with such devices.

The variation absolute dud describes a nuclear weapon that fails to explode.^[1] (A nuclear weapon which does explode, but does not achieve its expected power, is termed a fizzle.)

The term descends from the Middle English dudde, originally meaning worn-out or ragged clothing, and is a cognate of duds (i.e., "clothing") and dowdy. Eventually dud became a general pejorative for something useless, including ammunition.^[2]

By extension, "dud" has become a slang word for anything that does not work or is defective.

Generally your duds are "your last possessions", what you are wearing and carrying, so nice duds is ironic and possibly an oxymoron. Other meanings of 'dud' are:

• Duds - 16th century term for "clothes".
• Dud - 17th century term for "worthless". It is also a 17th century term for "old clothes" or "rags".
• Duddery - 17th to 19th century term for a "clothier's booth", trading in old cloth and rags.
• To sweat your duds - 19th century term for "to pawn one's clothes"
• Dudman - "Scarecrow!", possibly from Dutch Dood/dode man (dead man), or from the old clothes used to clothe a scarecrow.
• Milk Duds – Brand of caramel and cocoa confectionery

Look up dud or duds in Wiktionary, the free dictionary.

• Bomb disposal
• Firearm malfunction
• Unexploded ordnance