Military term for an issue that has been adressed over and over and over again. Comes from the expression ”You’re beating a dead horse.”, meaning that talking about the issue is not going to change anything so drop it.
Dead horse can also be used to describe words such as 1337, emo, and townie. There are already hundreds of similar defs for those terms, enough already their dead horses, stop beating them and move on.
Captain Snuffy - “Men, I’ve called this meeting here today to stress to you the importance of cleanliness in the barracks and to discuss the upcoming deployment to Iraq. Soldiers need to sweep out their rooms daily and...”
(2 hours later)
..and also I would like to be informed in writing when the troops have taken out the trash in the recreation room, and"
Sergeant – "SIR, WE’VE GOT IT!! It’s a dead freaking horse can we move on to other issues now?"