Synonyms and related words :
arbitrary, automatic, autonomous, discretional, discretionary, elective, free, free will, gratuitous, impulsive, independent, instinctive, involuntary, nonmandatory, offered, optional, proffered, self-acting, self-active, self-determined, self-determining, spontaneous, unasked, unbesought, unbidden, uncalled-for, uncoerced, uncompelled, unconscious, undesigned, unforced, unguarded, unguided, uninfluenced, unintended, unintentional, uninvited, unmeant, unmeditated, unplanned, unpremeditated, unpressured, unpurposed, unrequested, unrequired, unsolicited, unsought, unthinking, unthought-of, unwitting, voluntary, volunteer, willful