dooms·day / ˈdoōmzˌdā/ (also domes·day) • n. [in sing.] the last day of the world's existence. ∎ (in Christian belief) the day of the Last Judgment. ∎ fig. a time or event of crisis or great danger: [as adj.] in all the concern over greenhouse warming, one doomsday scenario stands out. PHRASES: till doomsday inf. forever: we'll be here till doomsday if you don't hurry up.