The Collaborative International Dictionary of English v.0.48:

Placation \Pla*ca"tion\, n. [L. placatio.]
   The act of placating. [R.] --Puttenham (1589).
   [1913 Webster]

WordNet (r) 3.0 (2006):

placation
    n 1: the act of placating and overcoming distrust and animosity
         [syn: placation, conciliation, propitiation]