reactEnglishOxford American Thesaurusreact verb 1 Ginny wondered how he would react if she told him the truth: behave, act, take it, conduct oneself, proceed; respond, reply, answer; retaliate; rare comport oneself. 2 it was perhaps no wonder that he reacted against this spartan, puritanical environment: rebel against, oppose, revolt against, rise up against.