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