Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
* extempŏrālĭtas, ātis, f. [extemporalis], the faculty of extemporaneous speaking or versifying, Suet. Tit. 3 (for which: extemporalis facultas, id. Aug. 84: facultas ex tempore dicendi, Quint. 10, 7, 1).