Formal:
* Improvisation: This is the most common and general term, referring to the spontaneous creation of something without preparation.
* Extemporaneous: This refers to speaking or performing without prior preparation, often relying on notes or outlines.
* Freestyling: This term is often used in music and spoken-word performance, implying creative improvisation within a specific style.
Informal:
* Winging it: This is a colloquial expression that implies doing something without a plan or preparation, often with a sense of risk.
* Making it up as you go along: This is a straightforward description of the process.
* Spontaneity: This term refers to the act of doing something without planning or premeditation.
The best term to use depends on the specific situation and the tone you want to convey.