/ Dictionary / Index B biological clock: Meaning and Definition of Find definitions for: biolog'ical clock' Pronunciation: [key] — Physiol. Physiol. an innate mechanism of the body that regulates its rhythmic and periodic cycles, as that of sleeping and waking. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. biological child biological control Related Content Daily Word Quiz: hedonist Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language