/ Dictionary / Index S sidereal time: Meaning and Definition of Find definitions for: side'real time' Pronunciation: [key] — Astron. Astron. time measured by the diurnal motion of stars. A sidereal day is about four minutes shorter than a solar day, with hours, minutes, and seconds all proportionally shorter. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sidereal month sidereal year Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language