once in a blue moon
/ˌwʌns ɪn ə ˌbluː ˈmuːn/
very rarely
“He only visits once in a blue moon.”
Origin: From rare astronomical occurrence of second full moon in calendar month, appearing bluish
/ˌwʌns ɪn ə ˌbluː ˈmuːn/
very rarely
“He only visits once in a blue moon.”
Origin: From rare astronomical occurrence of second full moon in calendar month, appearing bluish