noun

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

   “The announcement of the verdict brought a violent reaction.”

2. 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. Reactionary politics; a period in which reactionary thought or politics is resurgent or dominant.

Synonyms: reax, rxn