From Longman Dictionary of Contemporary EnglishDoomsdayDooms‧day /ˈduːmzdeɪ/ noun [uncountable] 1 → till/until Doomsday2 RFthe last day of the Earth’s existence, when everything will be destroyed, according to some religionsdoomsday scenario (=a description of a very bad and hopeless situation)
Examples from the Corpus
Doomsday• In 1987, I didn't have to concern myself about Doomsday scenarios as I was staying in Manchester.• Of course, if you choose a male tree you can wait until Doomsday and still never see a berry.doomsday scenario• A year ago, few people were talking about such a doomsday scenario.• One doomsday scenario: No Bonds, no stadium.• Admittedly, there is now much less reason for invoking this doomsday scenario. 