The Collaborative International Dictionary of English v.0.48:

Conciliator \Con*cil"i*a`tor\, n. [L.]
   One who conciliates.
   [1913 Webster]

WordNet (r) 3.0 (2006):

conciliator
    n 1: someone who tries to bring peace [syn: conciliator,
         make-peace, pacifier, peacemaker, reconciler]