done, made, brought about, undertaken, etc., of one's own accord or by free choice

a voluntary contribution.

of, pertaining to, or acting in accord with the will

voluntary cooperation.

of, pertaining to, or depending on voluntary action

voluntary hospitals.

Law .

acting or done without compulsion or obligation.

done by intention, and not by accident

voluntary manslaughter.

made without valuable consideration

a voluntary settlement.

Physiology . subject to or controlled by the will.

having the power of willing or choosing

a voluntary agent.

proceeding from a natural impulse; spontaneous

voluntary laughter.

something done voluntarily.

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.

adjective

forced , involuntary , obligatory , unwilling

adjective

autonomous , chosen , deliberate , designful , discretional , elected , free , freely , free-willed , gratuitous , honorary , independent , intended , intentional , opted , optional , spontaneous , unasked , unbidden , uncompelled , unconstrained , unforced , unpaid , unprescribed , volitional , volunteer , willed , willful , wished , witting , willing , uncompensated , unrecompensed , unremunerated , unsalaried , purposeful , elective , willingly