B2idiominformaltime
once in a blue moon
USUK
very rarely; almost never
Usually at the end of a sentence; a little playful. Natural in conversation, but examiners hear it constantly, so 'hardly ever' is safer in IELTS.
In context
I live far from my hometown, so I only see my cousins once in a blue moon.
My brother cooks dinner once in a blue moon, usually on Mother's Day.
Common mistake
Incorrect: once in the blue moon
Correct: once in a blue moon
More idioms about time
- around the clockall day and all night, without stopping
- at the last minuteat the latest possible time, just before something happens or must be done
- behind the timesold-fashioned; not using the newest ideas, methods or technology
- buy timeto delay something so that you have more time to prepare or decide
- for the time beingfor now, until something changes