Extemporaneous \Ex*tem`po*ra"ne*ous\, a. [See {Extempore}.] Composed, performed, or uttered on the spur of the moment, or without previous study; unpremeditated; off-hand; extempore; extemporary; as, an extemporaneous address or production. -- {Ex*tem`po*ra"ne*ous*ly}, adv. -- {Ex*tem`po*ra"ne*ous*ness},n.