Main Entry: re·act

Pronunciation: \rē-ˈakt\

Function: verb

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

Date: 1644

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 reactiontransitive verb : to cause to react