1. (adv.) Offhand; without previous study; extemporaneous; extempore; as, an impromptu speech\.

2. (n.) Something made or done offhand, at the moment, or without previous study; an extemporaneous composition, address, or remark.

3. (n.) A piece composed or played at first thought; a composition in the style of an extempore piece.

ad lib ad libitum ad-lib ad-libbing arrangement at short notice at sight by ear cadenza caught napping caught off balance caught short extemporaneous extemporaneously extemporaneousness extemporarily extemporariness extemporary extempore extemporization extemporized flourish haphazard hasty hot lick improvisation improvisatorial improvise improvised improvision improviso interpolation jury-rig jury-rigged lick makeshift measure off the cuff off the hip off-the-cuff offhand on sight out of hand playing by ear precipitate pro tempore quick riff rough-and-ready snap stopgap surprised taken aback taken by surprise taken unawares temporary arrangement temporary measure tripped up unarranged unbegun unconcocted uncontrived undeliberated undevised unhatched unmade unmanufactured unorganized unplanned unpremeditated unprepared unprimed unready unrehearsed unstudied vamp