Mitigation is the reduction of something harmful that has occurred or the reduction of its harmful effects. It may refer to measures taken to reduce the harmful effects of hazards that remain in potentia, or to manage harmful incidents that have already occurred. Definition of mitigation noun in Oxford Advanced Learner's Dictionary. Meaning , pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. MITIGATION meaning : 1. the act of reducing how harmful, unpleasant, or bad something is: 2. something that causes you…. Learn more. The meaning of MITIGATION is the act of mitigating something or the state of being mitigated : the process or result of making something less severe, dangerous, painful, harsh, or damaging. How to use mitigation in a sentence.