動詞 improvise:

1. perform without preparation
   同義詞：improvize, ad-lib, extemporize, extemporise
2. manage in a makeshift way; do with whatever is at hand
   同義詞：extemporize

1. If an actor forget his word, he have to improvise.
   演員要是忘記臺詞，那就只好即興現(xiàn)編。
2. The pianist forgot his music and had to improvise (the accompaniment).
   彈鋼琴的人把樂譜忘了，只好即興伴奏。
3. As we've not got the proper materials, we'll just have to improvise.
   我們沒有弄到合適的材料，只好臨時湊合了。

im.pro.vise

v.（動詞）
im.pro.vised,im.pro.vis.ing,im.pro.vis.es
v.tr.（及物動詞）
To invent, compose, or recite without preparation.
即興創(chuàng)作：無準(zhǔn)備地發(fā)明、創(chuàng)作或者背誦
To make or provide from available materials:
臨時提供，臨時湊成：用可利用的材料做或提供：
例句：
improvised a dinner for the unexpected guests; improvise a makeshift tourniquet.
為不速之客準(zhǔn)備晚餐；提供備用的止血帶

v.intr.（不及物動詞）
To invent, compose, recite, or execute something offhand.
即席創(chuàng)作; 即席表演：即興地發(fā)明、創(chuàng)作、背誦或者制成某事物

來源：
French improviser
法語 improviser
from Italian improvvisare
源自 意大利語 improvvisare
from improvviso [unforeseen]
源自 improvviso [沒有預(yù)見到的]
from Latin imprôvosus
源自 拉丁語 imprôvosus
in- [not] * see in-
in- [不] *參見 in-
prôvosus [past participle of] prôvidôre [to foresee] * see provide
prôvosus [] prôvidôre的過去分詞 [預(yù)見] *參見 provide

【引伸】
im.provis.er
n.（名詞）