This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. reducing, lessening the effects of something, generally something painful or uncomfortable

adj. Tending to mitigate or alleviate; mitigative.

Tending or having power to mitigate; alleviating; softening.

n. That which has power to mitigate or alleviate.

adj. moderating pain or sorrow by making it easier to bear

"The consternation of many is driven by the fact that in the absence of the mitigatory and ballasting influence of the U.S. presence, the central government in Baghdad may be powerless to stop men like Shaffir from turning their martial detachments into personal militias."

moderating   

mitigative    alleviatory