Noun
1. 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"2. 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"3. (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"4. an idea evoked by some experience;
"his reaction to the news was to start planning what to do"5. doing something in opposition to another way of doing it that you don't like;
"his style of painting was a reaction against cubism"6. extreme conservatism in political or social matters;
"the forces of reaction carried the election"7. (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"