dead letter

Definition of Dead Letter in English :

1. dead letter, non-issue

the state of something that has outlived its relevance

2. dead letter, dead mail

mail that can neither be delivered nor returned

WordNet Lexical Database for English. Princeton University. 2010.

Dead Letter

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a law or ordinance that is no longer enforced but has not been formally repealed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

1.

a law, practice, etc. no longer enforced or operative but not formally done away with

2.

a letter that cannot be delivered or returned, as because of incorrect address and lack of return address

n.

1. An unclaimed or undelivered letter that after a period of time is destroyed or returned to the sender by the postal service.

2. A law, rule, or precedent still formally in effect but no longer valid or enforced.