exculpation in WordNet English dictionary

1. a defense of some offensive behavior or some failure to keep a promise etc.
   "he kept finding excuses to stay"; "every day he had a new alibi for not getting a job"; "his transparent self-justification was unacceptable"
   excuse  alibi  exculpation  self-justification 
   
2. the act of freeing from guilt or blame
   exculpation