What does the idiom ‘once in a blue moon’ mean?

Explanation

‘Once in a blue moon’ is an idiom meaning that something happens very infrequently or rarely, as in ‘He only visits his hometown once in a blue moon.’ The phrase refers to the rare astronomical occurrence of a second full moon within a single calendar month, sometimes informally called a ‘blue moon,’ which happens only occasionally. Explore more English MCQs on mcqstutor to keep practicing.