The Collaborative International Dictionary of English v.0.48:

Redeemer \Re*deem"er\ (r?*d?m"?r), n.
   1. One who redeems.
      [1913 Webster]

   2. Specifically, the Savior of the world, Jesus Christ.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Redeemer
    n 1: a teacher and prophet born in Bethlehem and active in
         Nazareth; his life and sermons form the basis for
         Christianity (circa 4 BC - AD 29) [syn: Jesus, Jesus of
         Nazareth, the Nazarene, Jesus Christ, Christ,
         Savior, Saviour, Good Shepherd, Redeemer,
         Deliverer]
    2: someone who redeems or buys back (promissory notes or
       merchandise or commercial paper etc.)