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A person who immediately supports either physically, vocally, or interactively a cause or movement on the merit of how they feel about an issue or incident before all the facts surrounding the galvanizing issue or incident are completely known.
He was enraged at the apparent lack of concern for the feelings of those offended and immediately joined other reactivists on social media posting to get the offending party censured.
by Gramaticus January 15, 2016
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