/ Thesaurus / S Synonyms of sidereal day Find synonyms for: Noun1. sidereal day, day, time unit, unit of time, sidereal timeusage: the time for one complete rotation of the earth relative to a particular star, about 4 minutes shorter than a mean solar dayWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: labyrinth Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language