/im promp"tooh, -tyooh/ , adj.
1. made or done without previous preparation: an impromptu address to the unexpected crowds.
2. suddenly or hastily prepared, made, etc.: an impromptu dinner.
3. improvised; having the character of an improvisation.
adv.
4. without preparation: verses written impromptu.
n.
5. something impromptu; an impromptu speech, musical composition, performance, etc.
6. a character piece for piano common in the 19th century and having, despite its title, a clear-cut form.
[ 1660-70; in promptu in readiness; see IN, PROMPT ]
Syn. 1. See extemporaneous .