an extemporaneous speech or remark; "a witty impromptu must not sound premeditated";
a short musical passage that seems to have been made spontaneously without advance preparation;
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;