extemporize

 
Pronunciation: /ɪkˈstɛmpərʌɪz, ɛk-/
(also extemporise)

verb

[no object]
  • compose or perform something such as music or a speech without preparation; improvise: he extemporized at the piano [with object]: she was extemporizing touching melodies

Derivatives

extemporization

Pronunciation: /-ˈzeɪʃ(ə)n/
noun