extemporizing
v. 即兴创作,即席演奏( extemporize的现在分词 )
If you extemporize, you speak, act, or perform something immediately, without rehearsing or preparing it beforehand.
He completely departed from the text and extemporized in a very energetic fashion.
他完全脱稿,慷慨激昂地进行即席演说。