carried out with no preparation; impromptu.
Is extemporaneous an adjective?
EXTEMPORANEOUS (adjective) definition and synonyms | Macmillan Dictionary.
What is the word extempore mean?
on the spur of the moment; without premeditation or preparation; offhand: Questions were asked extempore from the floor. without notes: to speak extempore. (of musical performance) by improvisation. adjective. extemporaneous; impromptu.