adj. 25B6; adjective an extempore speech : IMPROMPTU, spontaneous, unscripted, ad lib, extemporary, extemporaneous; improvised, unrehearsed, unplanned, unprepared, off the top of one's head; informal off-the-cuff; formal ad libitum.
rehearsed.
25B6; adverb he was speaking extempore : SPONTANEOUSLY, extemporaneously, ad lib, without preparation, without rehearsal, off the top of one's head; informal off the cuff; formal ad libitum.