dead letter

noun

a law, ordinance, etc., that has lost its force but has not been formally repealed or abolished.
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-letter office) of a general post office.

Origin of dead letter

First recorded in 1570–80

OTHER WORDS FROM dead letter

dead-let·ter, adjective

Words nearby dead letter

dead in one's tracks, dead in the water, dead key, dead languages, dead leg, dead letter, dead letter box, dead lift, dead load, dead loss, dead mail

Example sentences from the Web for dead letter

British Dictionary definitions for dead letter

dead letter

noun

a letter that cannot be delivered or returned because it lacks adequate directions
a law or ordinance that is no longer enforced but has not been formally repealed
informal anything considered no longer worthy of consideration

Idioms and Phrases with dead letter

dead letter
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]