The Collaborative International Dictionary of English v.0.48:

Chiliasm \Chil"i*asm\, n. [Gr. ?, fr. ?. See Chiliad.]
   1. The millennium.
      [1913 Webster]

   2. The doctrine of the personal reign of Christ on earth
      during the millennium.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chiliasm
    n 1: belief in the Christian doctrine of the millennium
         mentioned in the Book of Revelations [syn:
         millenarianism, millenarism, millenniumism,
         chiliasm]