reaction Meaning, Definition & Usage

  1. noun (chemistry) a process in which one or more substances are changed into others
    chemical reaction.
    • there was a chemical reaction of the lime with the ground water
  2. noun an idea evoked by some experience
    • his reaction to the news was to start planning what to do
  3. noun a bodily process occurring due to the effect of some antecedent stimulus or agent
    response.
    • a bad reaction to the medicine
    • his responses have slowed with age
  4. noun (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
  5. noun 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
  6. noun extreme conservatism in political or social matters
    • the forces of reaction carried the election
  7. noun doing something in opposition to another way of doing it that you don't like
    • his style of painting was a reaction against cubism

WordNet

Re*ac"tion noun
Etymology
Cf. F. réaction.
Definitions
  1. Any action in resisting other action or force; counter tendency; movement in a contrary direction; reverse action.
  2. (Chem.) The mutual or reciprocal action of chemical agents upon each other, or the action upon such chemical agents of some form of energy, as heat, light, or electricity, resulting in a chemical change in one or more of these agents, with the production of new compounds or the manifestation of distinctive characters. See Blowpipe reaction, Flame reaction, under Blowpipe, and Flame.
  3. (Med.) An action included by vital resistance to some other action; depression or exhaustion of vital force consequent on overexertion or overstimulation; heightened activity and overaction succeeding depression or shock.
  4. (Mech.) The force which a body subjected to the action of a force from another body exerts upon the latter body in the opposite direction.
    Reaction is always equal and opposite to action, that is to say, the actions of two bodies upon each other are always equal and in opposite directions. Sir I. Newton (3d Law of Motion).
  5. (Politics) Backward tendency or movement after revolution, reform, or great progress in any direction.
    The new king had, at the very moment at which his fame and fortune reached the highest point, predicted the coming reaction. Macaulay.

Webster 1913