Dictionary

dead letter

noun

: a letter that cannot be delivered or returned by the post office because of an incorrect address or other problem

: a law or agreement that has lost its force or authority

Full Definition of DEAD LETTER

1
:  something that has lost its force or authority without being formally abolished
2
:  a letter that is undeliverable and unreturnable by the post office

First Known Use of DEAD LETTER

1627

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March 30, 2015
amphibology Hear it
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