Word.ws English Dictionary

X-Day

X-Day proper noun: 1 November 1945, the planned date for the Allied invasion of Kyushu in southwestern Japan in World War II (cancelled following Japan's unconditional surrender in September 1945).

Proper noun

X-Day

  1. (historical) 1 November 1945, the planned date for the Allied invasion of Kyushu in southwestern Japan in World War II (cancelled following Japan's unconditional surrender in September 1945).
  2. An annual celebration in the Church of the SubGenius parody religion, falling on July 5 and commemorating the prophesied end of the world on that date in 1998, when alien beings from "Planet X" were to have invaded.

Noun

X-Day (plural X-Days)

  1. Synonym of D-Day (“the date of any major event planned for the future”).
    Synonyms:
    D-Day

Synonyms of X-Day

Forms of X-Day

pluralX-Days
alternative formX-day

Questions about X-Day

What does X-Day mean?
X-Day means 1 November 1945, the planned date for the Allied invasion of Kyushu in southwestern Japan in World War II (cancelled following Japan's unconditional surrender in September 1945).
What part of speech is X-Day?
X-Day can be a proper noun or a noun.

Words near X-Day in the dictionary

  1. X-chairs
  2. X-chromosome
  3. X-chromosomes
  4. X-country
  5. X-craft
  6. X-Day
  7. X-Days
  8. x-direction
  9. X-disease
  10. x-div.
  11. x-dressing

Source and license

Adapted from Wiktionary: X-Day (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.

Last updated:

Cite this entry: “X-Day.” Word.ws, https://word.ws/x-day. Based on Wiktionary, CC BY-SA 4.0.