react

verb

re·​act rē-ˈakt 

reacted; reacting; reacts

intransitive verb

1

: to exert a reciprocal or counteracting force or influence

—often used with on or upon

2

: to change in response to a stimulus

3

: to act in opposition to a force or influence

—usually used with against

4

: to move or tend in a reverse direction

5

: to undergo chemical reaction

transitive verb

: to cause to react

Synonyms of react

• respond

Examples of react in a Sentence

When I told her what happened, she reacted with anger.

I didn't expect him to react that way.

The firefighters reacted quickly when they heard the alarm.

He reacted badly to the drug.

Recent Examples on the Web

Jalen Ramsey #5 of the Pittsburgh Steelers reacts during an NFL football game against the Cincinnati Bengals at Acrisure Stadium on November 16, 2025 in Pittsburgh, Pennsylvania. —Mike Darnay, CBS News, 17 Nov. 2025

My parents were so shocked that neither of them reacted visibly. —Madhuri Vijay, New Yorker, 16 Nov. 2025

Jack Brewer, a former special teams captain with the Minnesota Vikings, reacted to the shooting that reportedly left New York Jets cornerback Kris Boyd wounded on Sunday morning. —Ryan Gaydos , Jackson Thompson, FOXNews.com, 16 Nov. 2025

How big a step would that be and how would -- how should Democrats react to that? —ABC News, 16 Nov. 2025

Word History

Etymology

New Latin reactus, past participle of reagere, from Latin re- + agere to act — more at agent

First Known Use

1644, in the meaning defined at intransitive sense 1

Phrases Containing react

• react against

Rhymes for react

• abstract
• attacked
• attract
• contact
• contract
• detract
• distract
• enact
• exact
• extract
• hijacked
• impact

Kids Definition

react

verb

re·​act rē-ˈakt 

1

: to act or behave in response (as to stimulation or an influence)

the colonists reacted to the tax by boycotting tea

2

: to oppose a force or influence

—usually used with against

reacted against their unfair treatment

3

: to go through or cause to go through a chemical reaction

Medical Definition

react

intransitive verb

re·​act rē-ˈakt 

1

: to respond to a stimulus

2

: to undergo chemical reaction

transitive verb

: to cause to react