unpremeditated

adj

unstudied, undeliberated, unthought-out; unplanned, unplotted, unarranged, undesigned, unschemed, uncontrived; unintentional, unintended, unpurposive, undeliberate; unconscious, involuntary, automatic, immediate, instinctive, natural; unprepared, extemporaneous, extempore, impromptu, ad-lib, improvised, improvisational, improvisatory, off-the-cuff, off-the-top, shooting-from-the-hip, offhand; spontaneous, spur-of-the-moment, on-the-spot; impulsive, impetuous, madcap, hasty, rash, devil-may-care, reckless, blind.