Word.ws English Dictionary

that'll be the day

UK/ˌðætl̩ biː ðə ˈdeɪ/US/ˌðætl̩ bi ðə ˈdeɪ/

that'll be the day phrase: said in reply to something that one believes will never happen.

Phrase

that'll be the day

  1. (New Zealand, idiomatic, informal) Said in reply to something that one believes will never happen.
    • I’m going to get into work on time today. — That’ll be the day!
    • Transmission from Klingon ship: Federation ship Enterprise. Surrender and prepare to be boarded. / Jean-Luc Picard (Patrick Stewart): That will be the day.1990, Trent Christopher Ganino, Eric A. Stillwell, “Yesterday's Enterprise”, in Star Trek: The Next Generation, season 3, episode 15, spoken by Jean-Luc Picard (Patrick Stewart)

Synonyms of that'll be the day

Origin of that'll be the day

Originally referring to a significant day in the future regarded as worth waiting for.

Questions about that'll be the day

What does that'll be the day mean?
That'll be the day means said in reply to something that one believes will never happen.
What part of speech is that'll be the day?
That'll be the day is a phrase.
How do you pronounce that'll be the day?
That'll be the day is pronounced /ˌðætl̩ biː ðə ˈdeɪ/ (UK).

Words near that'll be the day in the dictionary

  1. that which has been seen cannot be unseen
  2. that will do
  3. that'd
  4. that'd've
  5. that'll
  6. that'll be the day
  7. that'll be the frosty Friday
  8. that'll do
  9. that'll do it to you
  10. that'll learn someone
  11. that'll teach someone

Source and license

Adapted from Wiktionary: that'll be the 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:

Pronunciation audio from Wikimedia Commons, each file under its own free license: En-au-that'll be the day.ogg.

Cite this entry: “that'll be the day.” Word.ws, https://word.ws/that%27ll_be_the_day. Based on Wiktionary, CC BY-SA 4.0.