impromptu

(s) 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
ad-lib, extemporaneous, extemporary, extempore, offhand, offhanded, off-the-cuff, unrehearsed,
(r) without advance preparation
- he spoke ad lib
ad lib, ad libitum, spontaneously,

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

ad-lib extemporaneous extemporary extempore offhand offhanded off-the-cuff unrehearsed ad libitum spontaneously