Last Day last·day uncommon noun 1. (New Testament) day of the Last Judgment when God will decree the fates of all men according to the good and evil of their earthly lives SynonymsJudgment DayJudgement DayDay of JudgmentDay of JudgementDoomsdayLast JudgmentLast JudgementLast Dayday of reckoningcrack of doomend of the world Related words Broader terms day WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.