Dictionary
reaction
noun re·ac·tion \rē-ˈak-shən\
: the way someone acts or feels in response to something that happens, is said, etc.
: an action or attitude that shows disagreement with or disapproval of someone or something
reactions : the ability to act and move quickly in order to avoid sudden danger
Full Definition of REACTION
1
a : the act or process or an instance of reacting b : resistance or opposition to a force, influence, or movement; especially : tendency toward a former and usually outmoded political or social order or policy
2
: a response to some treatment, situation, or stimulus <her stunned reaction to the news>; also : such a response expressed verbally <critical reaction to the play>
3
: bodily response to or activity aroused by a stimulus: a : an action induced by vital resistance to another action; especially : the response of tissues to a foreign substance (as an antigen or infective agent) b : depression or exhaustion due to excessive exertion or stimulation c : heightened activity and overaction succeeding depression or shock d : a mental or emotional disorder forming an individual's response to his or her life situation
4
: the force that a body subjected to the action of a force from another body exerts in the opposite direction
5
a (1) : chemical transformation or change : the interaction of chemical entities (2) : the state resulting from such a reaction b : a process involving change in atomic nuclei
See reaction defined for English-language learners
See reaction defined for kids
ADVERTISEMENT
First Known Use of REACTION
circa 1611
Rhymes with REACTION
abstraction, attraction, bolt-action, class action, compaction, contraction, cross action, detraction, diffraction, distraction, exaction, extraction, impaction, inaction, infraction, job action, live-action, olfaction, protraction, redaction, refraction, retraction, stop-action, subtraction, transaction
REACTION Defined for Kids
reaction
noun re·ac·tion \rē-ˈak-shən\
Definition of REACTION for Kids
1
: behavior or attitude in response to something <What was your reaction to the news?>
2
: a response of the body to a stimulus <He had an allergic reaction to peanuts.>
3
: a chemical change that is brought about by the action of one substance on another and results in a new substance being formed
Medical Dictionary
reaction
noun re·ac·tion \rē-ˈak-shən\
Medical Definition of REACTION
1
: the act or process or an instance of reacting
2
: bodily response to or activity aroused by a stimulus: a : an action induced by vital resistance to another action; especially : the response of tissues to a foreign substance (as an antigen or infective agent) b : depression or exhaustion due to excessive exertion or stimulation c : abnormally heightened activity succeeding depression or shock d : a mental or emotional disorder forming an individual's response to his or her life situation
3
: the force that a body subjected to the action of a force from another body exerts in the opposite direction
4
a (1) : chemical transformation or change : the interaction of chemical entities (2) : the state resulting from such a reaction b : a process involving change in atomic nuclei
Learn More About REACTION
Browse
Next Word in the Dictionary: reactionalPrevious Word in the Dictionary: reactantAll Words Near: reaction
ADVERTISEMENT
Seen & Heard
What made you want to look up reaction? Please tell us where you read or heard it (including the quote, if possible).