EXTEMPORA'NEOUS, adjective [Latin extemporaneus; ex and tempus, time.] Composed, performed or uttered at the time the subject occurs, without previous study; unpremeditated; as an extemporaneous address; an extemporaneous production; an extemporaneous prescription.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI