dead horse

noun
1.
something that has ceased to be useful or relevant.
Idioms
2.
beat/flog a dead horse, to persist in pursuing or trying to revive interest in a project or subject that has lost its usefulness or relevance.

Origin:
1820–30, Americanism

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To dead horse
Example sentences
In the illustration here they're feeding on a dead horse.
It is time to stop playing on the public's fears and quit flogging the dead
  horse.
Don't mean to kick a dead horse, but it seems it will help clarify points.
Objectively it should be a dead horse when it still can't produce positive
  results.
Idioms & Phrases
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature