A person or thing that is acting or capable of acting.

Any component that is not passive. See Passivity (engineering).

Having the power or quality of acting; causing change; communicating action or motion; acting;—opposed to passive, that receives.

"certain active principles"

Quick in physical movement; of an agile and vigorous body; nimble.

"an active child or animal"

In action; actually proceeding; working; in force

"active hostilities"

Given to action; constantly engaged in action; energetic; diligent; busy

"active mind"

Requiring or implying action or exertion

"active employment or service"

Given to action rather than contemplation; practical; operative

"an active rather than a speculative statesman"

Brisk; lively.

"an active demand for corn"

Implying or producing rapid action.

"an active disease"

(heading, grammar) About verbs.

(of source code) Eligible to be processed by a compiler or interpreter.

Not passive.

(gay sexual slang) (of a homosexual man) enjoying a role in anal sex in which he penetrates, rather than being penetrated by his partner.