Pronunciation: (ik-stem"pu-rā'nē-us),[key] —adj. 1. done, spoken, performed, etc., without special advance preparation; impromptu: an extemporaneous speech. 2. previously planned but delivered with the help of few or no notes: extemporaneous lectures. 3. speaking or performing with little or no advance preparation: extemporaneous actors. 4. made for the occasion, as a shelter.