Source : Webster's Revised Unabridged Dictionary (1913)

Mitigation \Mit`i*ga"tion\, n. [OE. mitigacioun, F. mitigation,
   fr. L. mitigatio.]
   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.

   Syn: Alleviation; abatement; relief.

Source : WordNet®

mitigation
     n 1: to act in such a way as to cause an offense to seem less
          serious [syn: {extenuation}, {palliation}]
     2: a partial excuse to mitigate censure; an attempt to
        represent an offense as less serious than it appears by
        showing mitigating circumstances [syn: {extenuation}]