1. (

• chemical_reaction ,
• reaction

) (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" ;

2. (

• reaction

) an idea evoked by some experience; "his reaction to the news was to start planning what to do" ;

3. (

• reaction ,
• response ,

) a bodily process occurring due to the effect of some antecedent stimulus or agent; "a bad reaction to the medicine"; "his responses have slowed with age" ;

4. (

• reaction

) (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. (

• reaction ,

) 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. (

• reaction ,

) extreme conservatism in political or social matters; "the forces of reaction carried the election" ;

7. (

• reaction ,

) doing something in opposition to another way of doing it that you don't like; "his style of painting was a reaction against cubism" ;