Once in a blue moonEnglishDescriptionVery rarely; very infrequently. Sources Wiktionary EquivalentsThis is how you express this idiom across languages and locales.ListMapChinese千載難逢not occurring once in a thousand yearsFrenchtous les trente-six du moisevery thirty-six of the monthItalianOgni morte di PapaOnce every Pope’s deathPolishraz na ruski rokonce in a Russian yearSpanishcada muerte de obispoeach death of a bishopLogin to correlate with other idioms