extemporization

ex·tem·po·rize

E0294700 (ĭk-stĕm′pə-rīz′)v. ex·tem·po·rized, ex·tem·po·riz·ing, ex·tem·po·riz·es v.tr. To do or perform (something) without prior preparation or practice: extemporized an acceptance speech.v.intr. To perform an act or utter something in an impromptu manner; improvise: "[When] the house lights dimmed, she could no longer read what she had written and was forced to extemporize" (Dale Peterson).

[From extempore.]

ex·tem′po·ri·za′tion (-pər-ĭ-zā′shən) n.ex·tem′po·riz′er n.

Thesaurus

Noun

extemporization - a performance given extempore without planning or preparationextemporisation, improvisationperformance - the act of presenting a play or a piece of music or other entertainment; "we congratulated him on his performance at the rehearsal"; "an inspired performance of Mozart's C minor concerto"