improvisation (n.) Look up improvisation at Dictionary.com
mid-15c., "unforeseen happening;" 1786 as "act of improvising musically," from French improvisation, from improviser "compose or say extemporaneously," from Italian improvvisare, from improvviso "unforeseen, unprepared," from Latin improvisus "not foreseen, unforeseen, unexpected," from assimilated form of in- "not, opposite of" (see in- (1)) + provisus "foreseen," also "provided," past participle of providere "foresee, provide" (see provide).