<p><strong>Noun</strong></p><ul><li>a person or thing that reacts or undergoes reaction</li><li>a device whose primary purpose is to introduce reactance into a circuit</li><li>a patient or animal that reacts positively towards a foreign material</li><li>nuclear reactor</li><li>a large container, as a vat, for processes in which the substances involved undergo a chemical reaction</li></ul>