/ˌæd ˈlɪb ||; ædˈ lɪb/adj advdone or spoken without preparation 临时；即席；即兴:
She had to speak ad lib because she couldn't find her notes. 她找不到讲稿，只好即兴发言。
ad lib verb [I] (
ad libbing;ad libbed)
The singer forgot the words so he had to ad lib. 歌手忘了词，所以只好临场发挥。