| 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. |
| 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. |