1. A span of 1000 years
   "The new millennium began in the year 2001";
   - millenary, chiliad
    
2. (New Testament) in the Book of Revelation it is foretold that those faithful to Jesus will reign with Jesus over the earth for a thousand years; the meaning of these words have been much debated; some denominations (e.g. Jehovah's Witnesses) expect it to be a thousand years of justice and peace and happiness
   "They believed the millennium would bring an end to all suffering"
    
3. The 1000th anniversary (or the celebration of it)
   "The city planned a grand celebration for its millennium";
   - millenary

Derived forms: millennia, millenniums

Type of: anniversary, day of remembrance, doctrine, ism, period, period of time, philosophical system, philosophy, school of thought, time period, time span

Encyclopedia: Millennium, North Carolina