Reverse Dictionary: VOLUNTARY

ADJECTIVES
ELECTIVE voluntary, optional, proceeding from free choice → 1643 obs.
ULTRONEOUS voluntary, made, offered, etc., of one’s own accord; spontaneous → 1637
VOLITIENT voluntary, willing; of one’s own free will or choice → 1844

ADVERBS
I-WALDES voluntarily; intentionally, of one’s own accord → a1000 obs.
ULTRONEOUSLY voluntarily; of one’s own accord; spontaneously → 1627

NOUNS
ULTRONEOUSNESS voluntary action; spontaneity → 1623