Definitions
1.VerbTo act in response."How did she react to the news?"
2.VerbTo act or perform a second time; to do over again; to reenact. .mw-parser-output .defdate{font-size:smaller}
3.VerbTo return an impulse or impression; to resist the action of another body by an opposite force"Every body reacts on the body that impels it from its natural state."
4.VerbTo act upon each other; to exercise a reciprocal or a reverse effect, as two or more chemical agents; to act in opposition.
5.VerbTo cause chemical agents to react; to cause one chemical agent to react with another.
6.VerbTo post a reaction (icon or emoji indicating how one feels about a posted message).
7.NounAn emoji used to express a reaction to a post on social media."Sad reacts only"