blue moon

blue moon

noun

Definition of BLUE MOON

a long or seemingly long period of time <once in a blue moon we'll get dressed up and eat in a fancy restaurant>

Synonyms aeon (or eon), blue moon, coon's age, cycle, donkey's years [chiefly British], eternity, forever, long, months, moon

Related Words infinity; lifetime

Near Antonyms flash, instant, jiffy, minute, moment, second, shake, split second, trice, twinkle, twinkling, wink; microsecond, nanosecond