/ Thesaurus / B Synonyms of blue moon Find synonyms for: Noun1. blue moon, long time, age, yearsusage: a long time; "something that happens once in blue moon almost never happens"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: aversion Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language