done, spoken, performed, etc., without special advance preparation; impromptu

an extemporaneous speech.

previously planned but delivered with the help of few or no notes

extemporaneous lectures.

speaking or performing with little or no advance preparation

extemporaneous actors.

made for the occasion, as a shelter.

adjective

deliberate , planned , premeditated , prepared , rehearsed

adjective

ad hoc , ad-lib , automatic , autoschediastic , by ear , casual , expedient , extemporary , extempore , fake , free , immediate , impromptu , improv , improvisatory , improviso , informal , jamming , made-up , makeshift , offhand , on impulse , on-the-spot , snap , spontaneous , spur-of-the-moment , toss off , toss out , unplanned , unpremeditated , unprepared , unrehearsed , unstudied , winging itnotes: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 lost , improvised