/ Dictionary / Index D diurnal circle: Meaning and Definition of Find definitions for: diur'nal cir'cle Pronunciation: [key] — Astron. Astron. the apparent circle described by a heavenly body as a result of one rotation by the earth. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. diurnal arc diurnal motion Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language