1》 moving or tending to move about vigorously or frequently.
↘(of a person's mind or imagination) alert and lively.
2》 participating in a particular sphere or activity.
3》 working or in operation.
4》 Grammar denoting a voice of verbs in which the subject is typically the person or thing performing the action and which can take a direct object (e.g. she loved him as opposed to he was loved ). The opposite of passive .
5》 (of a volcano) erupting or having erupted in historical times.
6》 (of a disease) not in remission or latent.
7》 having a chemical or biological effect on something.
8》 (of an electric circuit) capable of modifying its state or characteristics automatically in response to input or feedback.
■ noun Grammar an ~ form of a verb.
ME: from L. activus , from act- , agere 'act, do'.