If your remarks are extemporaneous, you have not prepared them in advance.

如果你的发言是即席的，说明你没有事先准备好。

At the Academy's annual Summit, Jobs gave a couple of short, extemporaneous talks to a roomful of promising young high school students.

在学的年上，乔布斯对一屋子前途无量的年轻高中生做了几次简短的即席演讲。