/doohmz"day'/ , n.
1. 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.
[ bef. 1000; ME domes dai, OE domesdaeg Judgment Day. See DOOM, DAY ]