The Oxford Thesaurus An A-Z Dictionary of Synonyms - reactionn.

1) response, reply, answer, effect, feedback: Did you get any reaction when you told her I had been arrested? Her reaction was to turn over and go back to sleep. 2) repulsion, resistance, counteraction, counterbalance, compensation: A rocket derives forward thrust by reaction against its own exhaust, hence can operate in a vacuum. 3) retaliation, reciprocation, reprisal, revenge: He shot her in reaction to her announcement that she was leaving him.