Voluntary

1. Done, given, or acting of one's own free will.
2. Done by design or intention; intentional.
3. Working or done without payment.
4. Endowed with the power of willing.
5. Of or relating to voluntarism.

Synonyms

• (acting of one's own free will): discretionary, optional, volitional
• (done by design or intention): intentional, willful
• (done without payment): honorary, pro bono, unpaid, unsalaried, unwaged
• (endowed with the power of willing): autonomous, spontaneous

Antonyms

• (all): involuntary
• (acting of one's own free will): compulsory, obligatory
• (done by design or intention): accidental
• (done without payment): paid, salaried