impromptu

英 [ɪm'prɒm(p)tjuː] 美[ɪm'prɑmptu]

• n. 即兴曲；即席演出
• adv. 即席地
• adj. 即席的

1. an extemporaneous speech or remark;

"a witty impromptu must not sound premeditated"

2. a short musical passage that seems to have been made spontaneously without advance preparation