The variation absolute dud describes a nuclear weapon that fails to explode.
Although dud rounds have failed to function as designed, they are still dangerous, and can explode if handled. In war-torn areas, many curious children have been injured or killed from tampering with such devices. Dud fireworks should be destroyed by soaking in water. No attempts to re-light them should be made. People should keep away from dud ammunition and should call proper authorities who can safely handle and remove it.
By extension, "dud" has become a slang word for anything that doesn't work or is defective. There is also a candy called Milk Duds, named for the fact that it was impossible to get them perfectly round.
"Duds" has also become popular slang for clothing, as in "Hey Faris, nice duds!"