(adj) with little or no preparation or forethought, Syn. extemporary, unrehearsed, extemporaneous, offhanded, extempore, offhand, impromptu, off-the-cuff, Example: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
The Collaborative International Dictionary of English (GCIDE) v.0.53 Collaborative International Dictionary (GCIDE)
adv. or a. [ F. impromptu, fr. L. in promptu in readiness, at hand; in in + promptus visibility, readiness, from promptus visible, ready. See Prompt. ] Offhand; without previous study; extemporaneous; extempore; as, an impromptu verse. [ 1913 Webster ]