once in a blue moon

once in a blue moon

very rarely. My sister lives in Alaska, so I only get to see her once in a blue moon. I don't know why I bought that CD-ROM for my computer - I only ever use it once in a blue moon.

See also: blue, moon, once

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once in a blue moon

almost never. Once in a blue moon I'll have a beer with friends, but it's not my regular drink.

Etymology: based on the informal phrase blue moon (= the second time in one month that you can see the full disk of the moon )

See also: blue, moon, once