very seldom, rarely
"Have you heard from Paul?" "Once in a blue moon he calls, maybe once a year."
ONCE IN A BLUE MOON
Meaning of ONCE IN A BLUE MOON in English
Wayne Magnuson. English idioms vocabulary. Словарь английских идиом. 2012
very seldom, rarely
"Have you heard from Paul?" "Once in a blue moon he calls, maybe once a year."
Wayne Magnuson. English idioms vocabulary. Словарь английских идиом. 2012