Lewis & Short

extempŏrālis, e, adj. [ex tempore, v. tempus, C.], on the spur of the moment, without preparation, extempore, extemporary, extemporaneous (post-Aug.; in Cic.: subitus, fortuitus): oratio, Quint. 4, 1, 54; 11, 2, 3: dictiones, id. 2, 4, 27: actio, id. 10, 7, 16: garrulitas, id. 2, 4, 15: facilitas, id. 10, 7, 18: temeritas, id. 10, 6, 6: audacia, Tac. Or. 6: facultas, Suet. Aug. 84: color, Quint. 10, 6, 5: figurae, Plin. Ep. 1, 20, 10: fortuna, Quint. 10, 6, 1: successus, id. 10, 7, 13: rhetor, Mart. 5, 54: contenti extemporali cibo, i. e. that easily provided, Lact. 1, 4, 6.
Adv.: extempŏrālĭter, extemporaneously, on the moment: scribere, Sid. Ep. 9, 14.