mitigation in WordNet English dictionary

1. to act in such a way as to cause an offense to seem less serious
   extenuation  mitigation  palliation 
   
2. a partial excuse to mitigate censure; an attempt to represent an offense as less serious than it appears by showing mitigating circumstances
   extenuation  mitigation 
   
3. the action of lessening in severity or intensity
   "the object being control or moderation of economic depressions"
   moderation  mitigation