Dud

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)), and small devices, have higher chances of being duds.

Duds are still dangerous, and can explode if handled. They have to be deactivated and disposed of carefully. In wartorn areas, many curious children have been injured or killed from tampering with such devices. Dud fireworks should never be destroyed by soaking in water as most fireworks becomes most unstable after water ingress.

The term descends from the Middle English dudde, meaning "ragged clothing", and had been in usage as a general pejorative for something worn-out or useless for several centuries prior to the widespread adoption of the fused explosive artillery shell.

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

By extension, "dud" has become a slang word for anything that does not work or is defective. There is also a candy called Milk Duds, so named because it was impossible to get them perfectly round.