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Meaning of sidereal time

side'real time'

Pronunciation: [key]
— Astron. Astron.
  1. 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.