What does "extempore" mean?

Extempore: Without previous study or meditation; without preparation; on the spur of the moment; suddenly; extemporaneously; as, to write or speak extempore. Shak. -- a. Done or performed extempore. "Extempore dissertation." Addison. "Extempore poetry." Dryden. -- n. Speaking or writing done extempore. [Obs.] Bp. Fell.