The Collaborative International Dictionary of English v.0.48:

Exoneration \Ex*on`er*a"tion\, n. [L. exoneratio: cf. F.
   Exon['e]ration.]
   The act of disburdening, discharging, or freeing morally from
   a charge or imputation; also, the state of being disburdened
   or freed from a charge.
   [1913 Webster]

WordNet (r) 3.0 (2006):

exoneration
    n 1: the condition of being relieved from blame or obligation
    2: the act of vindicating or defending against criticism or
       censure etc.; "friends provided a vindication of his
       position" [syn: vindication, exoneration]