from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A daily rhythmic activity cycle, based on 24-hour intervals, that is exhibited by many organisms.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The "internal body clock" that regulates the (roughly) 24-hour cycle of biological processes in animals and plants.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a daily cycle of activity observed in many living organisms
Sorry, no etymologies found.