/ Thesaurus / C Synonyms of circadian rhythm Find synonyms for: Noun1. circadian rhythm, biological timeusage: a daily cycle of activity observed in many living organismsWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: cosmology Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language