dead-letter
Preserved but no longer current.
An action of no value or weight; an article, owing to some mistake in its production, rendered utterly valueless,—often applied to any instrument in writing, which by some apparently trivial omission, becomes useless. At the general and large district post-offices, there is a department for letters which have been erroneously addressed, or for which, from many and various causes, there are no receivers.
Era: ca. 1874 (Victorian)
Sources & notes
Historical definition reproduced from Hotten’s The Slang Dictionary (1874, public domain; Project Gutenberg #42108, retrieved 2026-07-31). Reflects the attitudes of its era.
Common questions
What does “dead-letter” mean?
An action of no value or weight; an article, owing to some mistake in its production, rendered utterly valueless,—often applied to any instrument in writing, which by some apparently trivial omission, becomes useless. At the general and large district post-offices, there is a department for letters which have been erroneously addressed, or for which, from many and various causes, there are no receivers.
Is “dead-letter” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.