Meanings
- idiomaticnot comparableVery 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 7801 more example
[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 133Synonyms: once in a purple moon, rarely, seldom, infrequently, scarcely, seldomly, uncommonly, unoften
Synonyms & antonyms
adverbVery rarely; very infrequently.
Origin
See blue moon. First use appears c. 1833. See citation below.
Full word history & related roots →Translations
Chinese Cantonese 千載難逢 /千载难逢, 十年唔逢一閏 /十年唔逢一闰
- 千載難逢 /千载难逢 (cin¹ zoi² naan⁴ fung⁴)very rarely
- 十年唔逢一閏 /十年唔逢一闰 (sap⁶ nin⁴ m⁴ fung⁴ jat¹ jeon⁶)very rarely
Chinese Mandarin 千載難逢 /千载难逢
- 千載難逢 /千载难逢 (qiānzǎinánféng)very rarely
Czech jednou za uherský rok
- jednou za uherský rokvery rarely
Dutch eens in de zoveel tijd
- eens in de zoveel tijdvery rarely
Esperanto ege malofte
- ege maloftevery rarely
Finnish todella harvoin
- todella harvoinvery rarely
French tous les trente-six du mois, une fois toutes les lunes
- tous les trente-six du moisvery rarely
- une fois toutes les lunesvery rarely
German alle Jubeljahre
- alle Jubeljahrevery rarely
Greek στη χάση και στη φέξη
- στη χάση και στη φέξη (sti chási kai sti féxi)very rarely
Irish uair sna naoi n-aird, uair umá seach
- uair sna naoi n-airdvery rarely
- uair umá seachvery rarely
Italian una volta ogni morte di papa, ogni morte di papa
- una volta ogni morte di papavery rarely
- ogni morte di papavery rarely
Japanese ごくまれに
- ごくまれに (gokumare ni)very rarely
Polish raz na ruski rok, od wielkiego dzwonu
- raz na ruski rokvery rarely
- od wielkiego dzwonuvery rarely
Portuguese de vez em nunca, uma vez na vida, outra na morte
- de vez em nuncavery rarely
- uma vez na vida, outra na mortevery rarely
Russian раз в сто ле́т
- раз в сто ле́т (raz v sto lét)very rarely
Scottish Gaelic uair san ràith
- uair san ràithvery rarely
Slovak raz za uhorský rok
- raz za uhorský rokvery rarely
Spanish cada muerte de obispo, de guindas a brevas
- cada muerte de obispovery rarely
- de guindas a brevasvery rarely
- de higos a brevasvery rarely
- de Pascuas a Ramosvery rarely
- de ciento a vientovery rarely
- de ciento en vientovery rarely
- una vez a las quinientasvery rarely
- muy de vez en cuandovery rarely
Tamil அத்தி பூத்தாற் போல், ஆடிக்கு ஒரு முறை அமாவாசைக்கு ஒரு முறை
- அத்தி பூத்தாற் போல் (atti pūttāṟ pōl)very rarely
- ஆடிக்கு ஒரு முறை அமாவாசைக்கு ஒரு முறை (āṭikku oru muṟai amāvācaikku oru muṟai)very rarely
Thai มากไม่ค่อย
- มากไม่ค่อยvery rarely
Turkish kırk yılda bir
- kırk yılda birvery rarely
Vietnamese năm thì mười hoạ
- năm thì mười hoạvery rarely
Welsh unwaith yn y pedwar amser
- unwaith yn y pedwar amservery rarely
Cite this entry
once in a blue moon. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/once%20in%20a%20blue%20moon
“once in a blue moon.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/once%20in%20a%20blue%20moon. Accessed November 5, 2026.
WatkinsX Dictionary, s.v. “once in a blue moon,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/once%20in%20a%20blue%20moon.
Source: once in a blue moon on Wiktionary, CC BY-SA 4.0.