ad-lib
Definitions
To speak or perform in public without previously preparing one's words.
Something spoken, performed, or composed spontaneously without preparation.
Examples
The actor had to ad-lib his lines when he forgot the script during the live performance.
The comedian is famous for his ability to ad-lib hilarious jokes based on audience suggestions.
Synonyms
improvise extemporize wing it invent spontaneously unscripted off-the-cuff