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