arbitrary
autonomous
discretional
discretionary
elective
free
free will
gratuitous
independent
nonmandatory
offered
optional
proffered
self-acting
self-active
self-determined
self-determining
spontaneous
unasked
unbesought
unbidden
uncalled-for
uncoerced
uncompelled
unforced
uninfluenced
uninvited
unprompted
unrequested
unrequired
unsolicited
unsought
voluntary
volunteer
willful