from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun An unclaimed or undelivered letter that after a period of time is destroyed or returned to the sender by the postal service.
  • noun A law, rule, or precedent still formally in effect but no longer valid or enforced.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun An item of mail that cannot be delivered to its intended recipient; after some time it is returned to the sender, or destroyed
  • noun by extension A law that is no longer enforced

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun mail that can neither be delivered nor returned
  • noun the state of something that has outlived its relevance


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