American English

Definition of millennium noun from the Oxford Advanced American Dictionary



    (pl. millennia
    , (or )millenniums)
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  1. 1a period of 1,000 years, especially as calculated before or after the birth of Christ the second millennium A.D. For millennia, it was accepted that the earth was at the center of the universe.
  2. 2the millennium the time when one period of 1,000 years ends and another begins How did you celebrate the millennium?
See the Oxford Advanced Learner's Dictionary entry: millennium