<p><strong>Verb (used with object)</strong></p><ul><li>to make active; cause to function or act.</li><li>to render more reactive; excite: to activate a molecule.</li><li>to induce radioactivity.</li><li>to aerate (sewage) in order to accelerate decomposition of impure organic matter by microorganisms.</li><li>to make (carbon, a catalyst, molecules, etc.) more active.</li><li>to hasten (reactions) by various means, as heating.</li><li>to place (a military unit or station) on an active status in an assigned capacity.</li></ul><p><strong>Verb (used without object)</strong></p><ul><li>to become active or functional.</li></ul>