The Collaborative International Dictionary of English v.0.48:

Vaticinator \Va*tic"i*na`tor\, n. [L.]
   One who vaticinates; a prophet.
   [1913 Webster]

WordNet (r) 3.0 (2006):

vaticinator
    n 1: an authoritative person who divines the future [syn:
         prophet, prophesier, oracle, seer, vaticinator]