made or done without previous preparation

an impromptu address to the unexpected crowds.

suddenly or hastily prepared, made, etc.

an impromptu dinner.

improvised; having the character of an improvisation.

without preparation

verses written impromptu.

something impromptu; an impromptu speech, musical composition, performance, etc.

a character piece for piano common in the 19th century and having, despite its title, a clear-cut form.

adjective, adverb

deliberate , designed , planned , premeditated , rehearsed

adjective, adverb

ad-lib * , dashed off , extemporaneous , extempore , extemporized , fake , faked , improv , improviso , offhand , off the cuff * , played by ear , shot from the hip , spontaneous , spur-of-the-moment , thrown off , tossed off , unpremeditated , unprepared , unscripted , unstudied , vamped , whipped up , winged *notes:extemporaneous means \'prepared in advance and carried out with few or no notes\' while impromptu means \'totally unprepared , performed on the spur of the moment\' - but this distinction has been all but lostimpromptu conveys unrehearsed remarks or performance with an element of surprise , while extempore only suggests that this is done without notes or props

adjective

ad-lib , extemporary , extempore , improvised , offhand , snap , spur-of-the-moment , unrehearsed

noun

ad-lib , extemporization