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(dāng)場的，即興的，無準(zhǔn)備的：未經(jīng)或很少準(zhǔn)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(zhǔn)備的，當(dāng)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(shí)間]