—adj. 1. done, made, brought about, undertaken, etc., of one's own accord or by free choice: a voluntary contribution. 2. of, pertaining to, or acting in accord with the will: voluntary cooperation. 3. of, pertaining to, or depending on voluntary action: voluntary hospitals. 4. Law. a. acting or done without compulsion or obligation.
b. done by intention, and not by accident: voluntary manslaughter. c. made without valuable consideration: a voluntary settlement. 5. Physiol.subject to or controlled by the will.
6. having the power of willing or choosing: a voluntary agent. 7. proceeding from a natural impulse; spontaneous: voluntary laughter.
—n. 1. something done voluntarily.
2. a piece of music, frequently spontaneous and improvised, performed as a prelude to a larger work, esp. a piece of organ music performed before, during, or after an office of the church.