In-activate is a verb meaning to render something inactive or deactivate. Its antonyms are activate, energize, stimulate, and activate. Activate means to start, engage or set in motion something. Energize means to infuse energy or enthusiasm into something, or to boost its power. Stimulate means to encourage, excite or provoke an action or response. Reactivate means to re-establish or restore something to its active or operational state. These antonyms indicate actions that promote or restore vitality to something that has been inactive or dormant for some time.