A "dud" generally refers to something that fails to function as intended or is ineffective. In a military context, it commonly describes an ammunition round or explosive that does not fire or detonate properly, such as a misfired shell or an improvised explosive device that fails to explode.

In everyday language, "dud" can also mean a piece of clothing, especially rough or workwear, or personal belongings that are considered useless or ineffective. The term has a long history, originating from Middle English, originally meaning worn-out or ragged clothing, and later developing to mean anything that is useless or fails.

In summary:

• In military terms, a dud is an unexploded or faulty explosive.

• Informally, it refers to clothing or personal items that are considered no good or ineffective.

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