noun A period of time consisting of one thousand years.
noun The year in which one period of one thousand years ends and another begins, especially the year 2000.
A huge fireworks display was put on in Sydney to celebrate the millennium.
noun Any long (and possibly endless) era of universal happiness, peace, and prosperity, predicted by various people to come about someday.
expecting a millennium
proper noun The period of one thousand years during which Christ will reign on earth (according to Millenarianist interpretations).
usher in the millennium
proper noun A particular long (and possibly endless) era of universal happiness, peace, and prosperity, predicted by various people to come about someday.