What is the meaning of reaction?

noun

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