形容詞 extempore:

1. with little or no preparation or forethought
   同義詞：ad-lib, extemporaneous, extemporary, impromptu, offhand, offhanded, off-the-cuff, unrehearsed

副詞 extempore:

1. without prior preparation
   同義詞：extemporaneously, extemporarily

ex.tem.po.re

adj.（形容詞）
Spoken, carried out, or composed with little or no preparation or forethought.See Synonyms at extemporaneous
當場的，即興的，無準備的：未經(jīng)或很少準備或構(gòu)思而講的，做的或譜寫的參見 extemporaneous
adv.（副詞）
In an extemporaneous manner.
無準備的，當場的

來源：
Latin ex tempore
拉丁語 ex tempore
ex [of] * see ex-
ex […的] *參見 ex-
tempore [ablative of] tempus [time]
tempore [] tempus的奪格 [時間]