dead letter

American  

noun

1. a law, ordinance, etc., that has lost its force but has not been formally repealed or abolished.

2. a letter that cannot reach the addressee or be returned to the sender, usually because of incorrect address, and that is sent to and handled in a special division or department dead-letteroffice of a general post office.

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dead letter British  

noun

1. a letter that cannot be delivered or returned because it lacks adequate directions

2. a law or ordinance that is no longer enforced but has not been formally repealed

3. informal anything considered no longer worthy of consideration

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dead letter Idioms  

1. An unclaimed or undelivered letter that is eventually destroyed or returned to the sender. For example, She moved without leaving a forwarding address, so her mail ended up in the dead letter office . [c. 1700]

2. A statute or directive that is still valid but in practice is not enforced. For example, The blue laws here are a dead letter; all the stores open on Sundays and holidays . [Second half of 1600s]

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Other Word Forms

• dead-letter
  adjective

Etymology

Origin of dead letter

First recorded in 1570–80

Example Sentences

See Examples For:

dead letter

Every day that passes makes that resolution more of a dead letter, and adds to the elusiveness of a deal.

From The Wall Street Journal ● Oct. 23, 2025

This, Kagan says, renders impeachment and conviction virtually a dead letter.

From Salon ● Nov. 18, 2024

"As a result, the YCC framework seems to have become more of a dead letter."

From Reuters ● Oct. 31, 2023

If you don’t have effective enforcement, the law is a dead letter.

From Slate ● Sep. 18, 2023

As a case of independence the Kentish custom is quite complete, and manorial documents show on every page that it was anything but a dead letter.

From Villainage in England Essays in English Mediaeval History by Vinogradoff, Paul