Word.ws English Dictionary

once in a blue moon

/wʌns ɪn ə bluː muːn/

once in a blue moon adverb: very rarely; very infrequently.

Adverb

once in a blue moon (not comparable)

  1. (idiomatic) Very rarely; very infrequently.
    • We are no advocates for the eternal system of producing foreign operas to the exclusion of the works of English composers, but once in a blue moon such a thing may be allowed.1833, J. Lection (publisher), The Athenæum, page 780
    • [T]ime expanded and space contracted, and the name Blue Moon took on a symbolic meaning, as if the future, so delicately plausible, were of a kind that might happen once in a blue moon only.1933, James Hilton, Lost Horizon, published 1973, page 133

once in a blue moon meaning in Tamil, Malayalam, Thai and Vietnamese

once in a blue moon in Tamil

very rarely
அத்தி பூத்தாற் போல் atti pūttāṟ pōl, ஆடிக்கு ஒரு முறை அமாவாசைக்கு ஒரு முறை āṭikku oru muṟai amāvācaikku oru muṟai

once in a blue moon in Malayalam

rarely, hardly ever, scarcely ever
വല്ലപ്പോഴുമൊരിക്കൽ, വല്ലപ്പോഴും, വളരെ വിരളമായി, ചുരുക്കം അവസരങ്ങളിൽ, വളരെചുരുക്കമായി, അപൂർവ്വമായി

once in a blue moon in Thai

very rarely
มากไม่ค่อย

once in a blue moon in Vietnamese

very rarely
năm thì mười hoạ

Synonyms of once in a blue moon

All synonyms of once in a blue moon

Origin of once in a blue moon

See blue moon. First use appears c. 1833. See citation below.

Questions about once in a blue moon

What does once in a blue moon mean?
Once in a blue moon means very rarely; very infrequently.
What is once in a blue moon in Tamil?
Once in a blue moon in Tamil is அத்தி பூத்தாற் போல் (atti pūttāṟ pōl), ஆடிக்கு ஒரு முறை அமாவாசைக்கு ஒரு முறை (āṭikku oru muṟai amāvācaikku oru muṟai). See Once in a blue moon meaning in Tamil.
What part of speech is once in a blue moon?
Once in a blue moon is an adverb.
How do you pronounce once in a blue moon?
Once in a blue moon is pronounced /wʌns ɪn ə bluː muːn/.

Words near once in a blue moon in the dictionary

  1. Once Brewed
  2. once burned, twice cautious
  3. once burned, twice shy
  4. once for all
  5. once hurt, twice shy
  6. once in a blue moon
  7. once in a purple moon
  8. once in a way
  9. once in a while
  10. once in awhile
  11. once more

Source and license

Adapted from Wiktionary: once in a blue moon (page history and authors); once in a blue moon (Olam, E.K. Kurup corpus) (dataset and license). 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-once in a blue moon.ogg.

Cite this entry: “once in a blue moon.” Word.ws, https://word.ws/once_in_a_blue_moon. Based on Wiktionary, CC BY-SA 4.0.