1. Chiefly Philosophy and Theology. That engages in work or activity; that is in active operation. Now rare.With quot. 1751 cf. energy n. 3c, energizer n. 1.
2. Originally: that causes someone or something to engage in work or activity; that rouses or inspires someone to action. Now chiefly: that supplies energy (in various senses); esp. that fills someone or something with vigour, dynamism, or enthusiasm; invigorating, vitalizing; stimulating, exciting.
3. That supplies a device, machine, etc., with energy, esp. in the form of electricity, and thereby causes it (to begin) to operate.
► indicates date of composition for this text (as opposed to date of documentary evidence). More