Definition of "react"

react

/ɹiːˈækt/

verb
third-person singular simple present reacts, present participle reacting, simple past and past participle reacted
1. (intransitive) To act in response.
2. (transitive, now rare) To act or perform a second time; to do over again; to reenact.
  Quotations
  It is somewhat extraordinary, that the offence for which James II, was expelled, that of setting up power by assumption, should be re-acted, under another shape and form, by the parliament that expelled him.
  1791, Thomas Paine, Rights of Man
3. (physics, intransitive) To return an impulse or impression; to resist the action of another body by an opposite force
4. (chemistry, intransitive) To act upon each other; to exercise a reciprocal or a reverse effect, as two or more chemical agents; to act in opposition.
5. (chemistry, transitive) To cause chemical agents to react; to cause one chemical agent to react with another.
6. (Internet, intransitive) To post a reaction (icon or emoji indicating how one feels about a posted message).
noun
plural reacts
1. (Internet) An emoji used to express a reaction to a post on social media.