noun (n)

• to act in such a way as to cause an offense to seem less serious(noun.act)

  Synonym:
  extenuation, palliation
  

  source: wordnet30
• a partial excuse to mitigate censure; an attempt to represent an offense as less serious than it appears by showing mitigating circumstances(noun.communication)

  Synonym:
  extenuation
  

  source: wordnet30
• the action of lessening in severity or intensity(noun.act)

  Synonym:
  moderation
  

  source: wordnet30
• The act of mitigating, or the state of being mitigated; abatement or diminution of anything painful, harsh, severe, afflictive, or calamitous; as, the mitigation of pain, grief, rigor, severity, punishment, or penalty.(noun)

  source: webster1913