/ Dictionary / Index M millennium: Meaning and Definition of Find definitions for: mil•len•ni•um Pronunciation: (mi-len'ē-um), [key] — pl. -ni•ums, -ni•a a period of 1000 years. the period of a thousand years during which Christ will reign on earth. Rev. 20:1–7. a period of general righteousness and happiness, esp. in the indefinite future. a thousandth anniversary. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: millennium (Thesaurus) millennialism millepede Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language