be flogging a dead horse

be flogging a dead horse

To be continuing to focus on something, especially an issue or topic, that is no longer of any use or relevance. I don't know why you're flogging a dead horse—the rest of us have moved on from that problem.
See also: dead, flog, horse

be flogging a dead horse

BRITISH or

be beating a dead horse

AMERICAN
If someone is flogging a dead horse, they are wasting their time trying to achieve something that cannot be done. After putting in all that hard work it feels like we're flogging a dead horse — it's all very discouraging. You're beating a dead horse on this. These guys are defeated.
See also: dead, flog, horse
References in periodicals archive ?
I know it will seem to many to be flogging a dead horse, but every time she has another resounding success I can't help but think about the lost opportunity to have a landmark architectural symbol in Cardiff.
Martin Donnelly is confident there will be a positive reaction amongst the GAA public and Irish community throughout England to the decider in Ruislip on November 8, but admits that in the current climate, he "can't always be flogging a dead horse".
You can be enthusiastic about it but you can't always be flogging a dead horse."