(as|) dead as mutton

undoubtedly no longer alive or in existence

The idiom "dead as mutton" is believed to have originated in the 19th century, and it is a reference to the fact that mutton, which is the meat of an older sheep, becomes tough and less flavorful after it has been slaughtered. This expression is used to imply that it is unquestionably lifeless or inanimate, with no chance of revival or recovery, just like the meat from a sheep that has been killed.

When the batteries in the remote control died, it was as dead as mutton, and we couldn't change the channel.
After the old refrigerator stopped working, it became as dead as mutton, and all the food inside spoiled.
The abandoned factory on the outskirts of town is as dead as mutton, with no signs of life or activity.
The outdated software had so many bugs and glitches that it was dead as mutton in terms of usability.
The proposal for the new project was rejected by the investors, leaving the idea dead as mutton.

not functional or in general use anymore

The exact origin of the idiom "dead as mutton" is uncertain, but it likely stems from the perception that mutton (the meat of mature sheep) becomes tough and less desirable after being slaughtered. Therefore, likening something to being "dead as mutton" suggests that it is completely defunct or no longer useful, much like the meat of a sheep that has been slaughtered.

After years of neglect, the old factory was now dead as mutton, with broken machinery and empty halls.
The company's outdated business model rendered it as dead as mutton in the modern market.
The once-popular gadget is now dead as mutton, overshadowed by newer, more advanced technology.
The decrepit mansion had fallen into disrepair, its grandeur now dead as mutton, a relic of a bygone era.