IMPROMPTU
extemporaneous, ad-lib, extemporary, extempore, impromptu, offhand, offhanded, off-the-cuff, unrehearsed
(adjective) 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”
impromptu
(noun) an extemporaneous speech or remark; “a witty impromptu must not sound premeditated”
impromptu
(noun) a short musical passage that seems to have been made spontaneously without advance preparation
Source: WordNet® 3.1
Etymology
Adjective
impromptu (not comparable)
Improvised; without prior preparation, planning or rehearsal.
Synonyms: extemporaneous, unplanned, Thesaurus:impromptu
Noun
impromptu (plural impromptus)
(music) A short musical composition for an informal occasion often with the character of improvisation and usually to be played solo.
(by extension) Any composition, musical or otherwise, that is created on the spot without preparation.
Source: Wiktionary
Im*promp"tu, adv. or a. Etym: [F. impromptu, fr. L. in promptu in
readiness, at hand; in in + promptus visibility, readiness, from
promptus visible, ready. See Prompt.]
Definition: Offhand; without previous study; extemporaneous; extempore; as,
an impromptu verse.
Im*promp"tu, n.
1. Something made or done offhand, at the moment, or without previous
study; an extemporaneous composition, address, or remark.
2. (Mus.)
Definition: A piece composed or played at first thought; a composition in
the style of an extempore piece.
Source: Webster’s Unabridged Dictionary 1913 Edition