没彩排过的；没有提前准备过的；

1. with little or no preparation or forethought

    e.g. his ad-lib comments showed poor judgment
           an extemporaneous piano recital
           an extemporary lecture
           an extempore skit
           an impromptu speech
           offhand excuses
           trying to sound offhanded and reassuring
           an off-the-cuff toast
           a few unrehearsed comments

    Synonym: ad-libextemporaneousextemporaryextemporeimpromptuoffhandoffhandedoff-the-cuff