ad-lib caught napping caught off balance caught short extemporaneous extemporized haphazard hasty impromptu improvised inadvertent makeshift precipitate rough-and-ready snap surprised taken aback taken by surprise taken unawares tripped up unarranged unbegun unconcocted uncontrived undeliberated undesigned unhatched unintended unmade unmanufactured unorganized unplanned unpremeditated unprepared unprimed unpurposed unready unstudied unthought