[n] doing something in opposition to another way of doing it that you don't like; "his style of painting was a reaction against cubism"
[n] a bodily process occurring due to the effect of some foregoing stimulus or agent; "a bad reaction to the medicine"; "his responses have slowed with age"
[n] an idea evoked by some experience; "his reaction to the news was to start planning what to do"
[n] extreme conservatism in political or social matters; "the forces of reaction carried the election"
[n] a response that reveals a person's feelings or attitude; "he was pleased by the audience's reaction to his performance"; "John feared his mother's reaction when she saw the broken lamp"
[n] (mechanics) the equal and opposite force that is produced when any force is applied to a body; "every action has an equal and opposite reaction"
[n] (chemistry) a process in which one or more substances are changed into others; "there was a chemical reaction of the lime with the ground water"