Improvisation

Etymology

From Italian "improvvisare" and French, ultimately from Latin "improvisus" (unforeseen), built from "in-" (not) plus "provisus," past participle of "providere" (to foresee, provide). To improvise is literally to act on the unforeseen — without prior provision.

noun · /im-prov-uh-ZAY-shuhn/
Composing or performing in the moment, without a fixed score or script.
What it names
The discipline of making art live and unrepeatable — the skill behind a jazz solo or an unscripted scene — which is real craft, not mere winging it.
Example
The written tune lasted ninety seconds; the rest of the track was pure improvisation.
Related idea
Improvisation invents within a form on the spot; composition fixes choices in advance to be reproduced. A jazz standard is a composition; what a soloist does over it is improvisation.