To move in opposition or in retaliation.
A move in opposition or response to a preceding move.
To act in response.
To act upon each other; to exercise a reciprocal or a reverse effect, as two or more chemical agents; to act in opposition.
To post a reaction (icon or emoji indicating how one feels about a posted message).
To return an impulse or impression; to resist the action of another body by an opposite force
To cause chemical agents to react; to cause one chemical agent to react with another.
An emoji used to express a reaction to a post on social media.