Blue moon

Blue moon is a slang term that is commonly used to refer to something that happens very rarely or once in a while.

In more detail, the phrase “blue moon” originated from the uncommon occurrence of having a second full moon within a calendar month. Since a blue moon is a rare event, this term is often used to describe any situation or event that happens infrequently or once in a blue moon.

Example 1: “I hardly ever go to the beach, but once in a blue moon, I’ll make an exception and spend a day by the ocean.”

Example 2: “My favorite band rarely performs live, so when they announced a concert in my city, I knew I couldn’t miss it. Their shows are a blue moon occurrence!”