‘Once in A Blue Moon’: Definition, Meaning and Examples

Have you heard someone say that something happens ‘once in a blue moon’? Are you unsure of what that means? We’ll cover that in this article, plus teach you how to use the phrase in a sentence correctly.

In short:

• ‘Once in a blue moon’ means rarely or once in a very long time.

Essentially, it means every once in a while or not very often.

What Does ‘Once in a Blue Moon’ Mean?

‘Once in a blue moon’ is a common American phrase that means ‘every once in a while’ or ‘not that often.’ It’s used as a way to say that you don’t do something that frequently.

You might hear people say:

• They go on vacation once in a blue moon.
• They get out of the house only once in a blue moon.

It simply means that they don’t have the time to do those things as much as they’d like.

In Season 1, episode 8 of Grey’s Anatomy, while Izzy’s talking on the phone, Meredith’s voiceover says:

"Once in a blue moon, people will surprise you."

In this particular scene, Meredith is talking about how Izzy finally decides to call her mom after resisting for so long, which is surprising because of how she hides her trailer park upbringing for most of the show.

In Season 2, episode 9 of Sex and the City, Carrie’s voice-over says:

"…but once in a blue moon, you can change a woman."

In this case, Carrie is talking about her best friend, Miranda, and how Steve was able to change her. She’s saying that kind of thing only happens once in a blue moon.

Where Does ‘Once in a Blue Moon’ Come From? 

The phrase ‘once in a blue moon’ comes from:

• The second but rare appearance of the full moon in the same month.
• The second appearance of the moon makes it look blue.
• This phenomenon only happens once every 32 months.

Sometimes, there are two blue moons in a year, but this only happens once every 19 years.

The first recorded use of the phrases was in 1528 when William Roy and Jeremy Barlowe published an anti-clerical pamphlet that included the phrase:

'If they say the moon is [blue], it must be true.'

Later, the expression was used in situations that implied that someone was a fool or too gullible.

The phrase didn’t come back into circulation again until the 19^th century when Pierce Egan published Real Life in London.

At the time of publication, the phrase meant:

• Close to impossible
• Rarely

Examples of ‘Once in a Blue Moon’ in Sentences 

How would you use ‘once in a blue moon’ in a sentence?

Let’s see some examples:

• Once in a blue moon, I like to go out on the lake and just let the river guide me. Sometimes, I just sit and read, sometimes I watch something on my tablet.
• Time flies when you haven’t seen your family in a while. I only see them once in a blue moon. I really need to be better about it.
• Mrs. Thompson always said that she only goes hiking once in a blue moon. She said her wife needed her on the weekend. Apparently, she’s wheelchair-bound.
• I get my hair done once in a blue moon because my money goes to other things. I have four kids, and I own my own home, so I have a lot of expenses. It’d be nice to have a full spa day to myself.
• I’d love to be able to go on more than one vacation every year. But my job just doesn’t give me enough paid time off. I need to get a side gig.
• We take a trip to see my mom once in a blue moon. The kids always have a good time, but she just lives so far away. Maybe we could get her to move closer.
• We clean the attic out once in a blue moon. My auntie used to do it with my mom before she passed away, but now my mom just can’t bring herself to do it as often as she used to.
• I go to the mall every once in a blue moon. I just don’t like being around too many people at once. It gives me anxiety, and I want to leave immediately.

Other Ways to Say ‘Once in a Blue Moon’

What other words or phrases convey the same meaning as ‘once in a blue moon’?

Let’s see some examples:

• Barely
• Rarely
• Seldom
• Almost never
• Hardly ever
• Scarcely ever
• Very seldom
• Infrequently
• On rare occasions
• Not often
• Sporadically
• Occasionally
• Hardly
• Uncommonly
• Once in a while
• Sometimes
• On and off
• In a few cases
• Every now and then
• From time to time
• Now and then
• Irregularly/not regularly
• Not all the time
• Semi-occasionally
• Not too often
• Not much

Concluding Thoughts on ‘Once in a Blue Moon’

To recap, we learned the following:

• ‘Once in a blue moon’ means rarely or once in a very long time.

Remember, it means every once in a while or not very often.

If you ever get stuck on anything, you can always come back here to review what you learned. We’ve got a whole library of content on other idioms you might want to check out while you’re learning the language. It could be useful, so feel free to check it out whenever you want.