"Voluntary" is a word in LAW AND LEGAL, ENGLISH

Free; without compulsion or solicitation

One who advocates voluntaryism.

One who engages in any affair of his own free will; a
volunteer.

Of or pertaining to the will; subject to, or
regulated by, the will; as, the voluntary motions of an animal, such as
the movements of the leg or arm (in distinction from involuntary
motions, such as the movements of the heart); the voluntary muscle
fibers, which are the agents in voluntary motion.

Free; without compulsion; according to the will,
consent, or agreement, of a party; without consideration; gratuitous;
without valuable consideration.

Proceeding from the will; produced in or by an act of
choice.

A piece played by a musician, often extemporarily,
according to his fancy; specifically, an organ solo played before,
during, or after divine service.

Unconstrained by the interference of another;
unimpelled by the influence of another; not prompted or persuaded by
another; done of his or its own accord; spontaneous; acting of one's
self, or of itself; free.

Done by design or intention; intentional; purposed;
intended; not accidental; as, if a man kills another by lopping a tree,
it is not voluntary manslaughter.

Of or pertaining to voluntaryism; as, a voluntary
church, in distinction from an established or state church.

Endowed with the power of willing; as, man is a
voluntary agent.