1. 即席的：extemporary 无准备的 | extempore 即席的 | extemporization 即席作成

2. 即席之作：extemporarilyoffhandedly 即席地 | extempore 即席之作 | extemporeon-the-spot 即席

3. 即席的、無準備的：contemporary 同時代的人物 | extempore 即席的、無準備的 | terrestrial 陸地上的

4. 即席的; 当场的 (形)：extemporary 无准备的; 随口说的 (形) | extempore 即席的; 当场的 (形) | extension cord 延长线

adj

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-libextemporaneousextemporaryimpromptuoffhandoffhandedoff-the-cuffunrehearsed