adv. without prior preparation; "he spoke extemporaneously"

adj. with little or no preparation or forethought; "his ad-lib comments showed poor judgment"; "an extemporaneous piano recital"; "an extemporary lecture"; "an extempore skit"; "an impromptu speech"; "offhand excuses"; "trying to sound offhanded and reassuring"; "an off-the-cuff toast"; "a few unrehearsed comments"

adj. unprepared and unable to react quickly; "the new product caught their competitors flat-footed"

adj. in response to an unforeseen need; "a spur-of-the-moment party"