Dictionary

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.

Example: certain active principles

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

Example: an active child or animal

In action; actually proceeding; working; in force

Example: active hostilities

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

Example: active mind