apocalypse
n. countablen. a very big event that causes total destruction or the end of the world. People also use it to describe a huge disaster that changes everything.
n. the complete final destruction of the world, or an event involving destruction or damage on an awesome, catastrophic scale. Often used metaphorically to describe a total collapse of a system or society.
Many movies show what happens after a global apocalypse.
The stock market crash felt like a financial apocalypse to the investors who lost their savings.
Proprialization from apocalypse, ultimately from Ancient Greek ἀποκάλυψις (apokálupsis, “revelation”). The translation decisions, from the original Greek to the conventional English choices Revelation and Apocalypse, are covered by Wikipedia at Book of Revelation § Title, authorship, and date.
Often used with the definite article ('the apocalypse') when referring to the end of the world.