Definition of "reaction" in English

noun

1. An action or statement in response to a stimulus or other event.

   • The announcement of the verdict brought a violent reaction.
   • You were in the courtroom. What is your reaction?
   • When I last tried to eat strawberries I had a terrible allergic reaction.

2. (chemistry) A transformation in which one or more substances is converted into another by combination or decomposition.

   • In this reaction, the acid and base will neutralize each other, producing a salt.

3. (politics) Reactionary politics; a period in which reactionary thought or politics is resurgent or dominant.

4. (Misesian praxeology, Austrian economics) Unpurposeful behavior.

5. (Internet) An icon or emoji appended to a posted message by a user to express their feeling about it.