Entry 2 senses · 2 variants Webster, 1913 Millenarian · Mil·le·na·ri·an · IPA /mɪlɪˈnɛːɹɪən/ a. n. 01 a. Consisting of a thousand years; of or pertaining to the millennium, or to the Millenarians. 1. Consisting of a thousand years; of or pertaining to the millennium, or to the Millenarians. 02 n. One who believes that Christ will personally reign on earth a thousand years; a Chiliast. 1. One who believes that Christ will personally reign on earth a thousand years; a Chiliast.