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