The Collaborative International Dictionary of English v.0.48:

Propitiate \Pro*pi"ti*ate\, v. t. [imp. & p. p. Propitiated;
   p. pr. & vb. n. Propitiating.] [L. propitiatus, p. p. of
   propitiare to propitiate, fr. propitius favorable. See
   Propitious.]
   To appease to render favorable; to make propitious; to
   conciliate.
   [1913 Webster]

         Let fierce Achilles, dreadful in his rage,
         The god propitiate, and the pest assuage. --Pope.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Propitiate \Pro*pi"ti*ate\, v. i.
   To make propitiation; to atone.
   [1913 Webster]

WordNet (r) 3.0 (2006):

propitiate
    v 1: make peace with [syn: propitiate, appease]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "propitiate":
   adapt, adjust, allay, appease, assuage, atone, atone for, calm,
   compensate, conciliate, conform, content, cool, defuse, dulcify,
   expiate, give satisfaction, immolate before, intercede, lay,
   lay the dust, live down, make amends, make compensation, make good,
   make matters up, make propitiation, make reparation, make right,
   make sacrifice to, make up for, mediate, mollify, offer sacrifice,
   pacify, pay the forfeit, pay the penalty, placate, pour balm on,
   recompense, reconcile, redeem, redress, repair, sacrifice, satisfy,
   smooth, smooth down, smooth over, soothe, square it, square things,
   sweeten, tranquilize