"Existential threat" means something so devastating it threatens the subjects very existence.

It's meant that for as long as the phrase has been in use.

> an existential threat is a threat to the existence of something.

I can't decide if this comment is very clever ironic satire or... not ;-)

> Politicians started using that phrase en masse about a year ago

"Existential threat" has been in wide-spread use for a really long time. The first time I heard the phrase used was probably some time in the late 90s. And that's more a function of my age than of how long the term has been used. The cliche is at least half a century old and has been used by politicians for at least decades.

For example, the phrase was commonly used in anti-proliferation and denuclearization advocacy during the last quarter of the 20th century, when nuclear weapons were characterized as an "existential threat" to humanity. This use persists today; see, for example, https://www.start.umd.edu/publication/nuclear-weapons-and-ex...

But the term isn't particularly partisan or limited to extinction-level threats. it's also been used throughout modern history by right-wing populists to refer to one group or another being an "existential threat to our way of life". See for example https://www.bbc.com/news/world-us-canada-44498438

The point is, the phrase has been used for a long time, always with the same meaning, and its use hasn't been particularly partisan as far as I can ever remember. Both sides use the phrase for various things. But they all definitely mean the same thing -- a threat to the existence of something (humanity, dominant cultural norms, the country, etc.). Not a "perceived" threat.

I'm genuinely and sincerely curious where you got the idea that "Existential threat means an implied, or perceived threat" rather than "a threat to the existence of a thing". The former has never been anywhere close to the dominant accepted meaning. Possibly you heard a politician or pundit use the term in a sarcastic way and misunderstood their sarcasm as literal? Or you heard someone use the phrase in a hyperbolic way?

Can you share one or more sources where people are using the phrase in the way you describe?