adj.即席的;临时的;无准备的;
例句:
His call for a book of the trains had been a sheer piece of impromptu.
他打听火车时刻表只是一段纯粹的即兴曲.
The President gave an impromptu press conference.
总统临时举行记者招待会.
I'm sure his remarks were rehearsed, not impromptu.
我肯定他的话是预先想好的, 不是即席讲的.