From χίλιοι [chilioi] (Rev. Rev. 20:3+), one thousand . The belief in a literal one thousand year reign of Christ upon the earth (Rev. Rev. 20:4-6+). The most explicit reference in Scripture to the thousand-year millennial reign of Christ is found in Revelation Rev. 20:1+. It is a significant fact that the early adherents of premillennialism (or chiliasm, as it was first called), either had direct contact with John, the longest living apostle, or with his most famous disciple Polycarp.1 See Premillennial.
1 Larry V. Crutchfield, Revelation in the New Testament, in Mal Couch, ed., A Bible Handbook to Revelation (Grand Rapids, MI: Kregel Publications, 2001), 24.