Select the most appropriate meaning of the given idiom.

Once in a blue moon

Very rarely

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

This idiom is used to describe something that happens very infrequently, or only once in a very long time. It is often used to express surprise or disbelief that something has happened at all.

The other options for the meaning of the idiom are not as accurate.

• Occasionally means happening from time to time, but not very often.
• Frequently means happening often.
• Incessantly means happening continuously, without stopping.