Select the most appropriate meaning of the given idiom.

Once in a blue moon

Rarely

The most appropriate meaning of the idiom "once in a blue moon" is rarely.

This idiom means something that happens very infrequently. It is often used to describe something that is so rare that it is almost impossible to happen. The idiom comes from the fact that a blue moon is a second full moon in a month. This happens very rarely, about once every 32 months.

Here are some examples of how the idiom "once in a blue moon" can be used in a sentence:

• He gets a raise once in a blue moon.
• I see my relatives once in a blue moon.
• It snows once in a blue moon in this city.