re‧ac‧tion S2 W2

to a situation/event

[uncountable and countable] something that you feel or do because of something that has happened or been said [↪ response]:
What was Jeff's reaction when you told him about the job?
reaction to
the government's reaction to the fuel crisis
bring/provoke/produce a reaction
The news brought an angry reaction from unions.
somebody's first/immediate reaction
His first reaction was to deny everything.
instinctive/gut reaction (=what you immediately feel before you have time to think)
My gut reaction was not to trust him.
There were mixed reactions (=different people reacting in different ways) to the strike.
in reaction to something
An emergency fund was set up in reaction to the famine.

moving quickly


[plural] your ability to move quickly when something dangerous happens suddenly:
a skilled driver with very quick reactions

to food/drugs

[countable]MIMD if you have a reaction to a drug or to something you have eaten, it makes you ill
reaction to
a reaction to the immunization
cause/bring on/trigger a reaction
Certain foods are more likely than others to cause allergic reactions.


[uncountable and countable]
a) HC a chemical change that happens when two or more substances are mixed together:
a chemical reaction in the soil
b) HP a physical force that is the result of an equally strong physical force in the opposite direction


[singular] a change in people's attitudes, behaviour, fashions etc that happens because they disapprove of the way in which things were done in the past
reaction against
a reaction against the traditional values of the nineteenth century

against change

[uncountable] formalPPP strong and unreasonable opposition to all social and political changes:
The revolutionary movement was crushed by the forces of reaction.

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