|—vb (foll by against)|
|2.||to act in an opposing or contrary manner|
|3.||(intr) physics to exert an equal force in the opposite direction to an acting force|
|4.||chem to undergo or cause to undergo a chemical reaction|
|[C17: from Late Latin reagere, from |
react re·act (rē-ākt')
v. re·act·ed, re·act·ing, re·acts
To act in response to a stimulus.
To undergo a chemical reaction.