Doomsday

UK: /ˈduːmzdeɪ/ US: /ˈdumzˌdeɪ/ ,(do̅o̅mz′dā′)

WordReference Random House Learner's Dictionary of American English © 2026

dooms•day /ˈdumzˌdeɪ/   n. 

1. Religion [proper noun] the day of the Last Judgment, at the end of the world.
2. nuclear destruction of the world:
   [uncountable] a story about doomsday in the near future.

WordReference Random House Unabridged Dictionary of American English © 2026

dooms•day  (do̅o̅mz′dā′), n. 

1. Religion the day of the Last Judgment, at the end of the world.
2. any day of judgment or sentence.
3. nuclear destruction of the world.

adj. 

4. given to or marked by forebodings or predictions of impending calamity;
   esp. concerned with or predicting future universal destruction:
   the doomsday issue of all-out nuclear war.
5. capable of causing widespread or total destruction:
   doomsday weapons.

• Middle English domes dai, Old English dōmesdæg Judgment Day. See doom, day bef. 1000

Collins Concise English Dictionary © HarperCollins Publishers::

doomsday, domesday / ˈduːmzˌdeɪ/ noun

1. (sometimes capital) the day on which the Last Judgment will occur
2. any day of reckoning
3. (modifier) characterized by predictions of disaster: doomsday scenario

Etymology: Old English dōmes dæg Judgment Day; related to Old Norse domsdagr