The Collaborative International Dictionary
Extemporaneousness
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; ad-lib; extempore; extemporary; as, an extemporaneous address or production. -- Ex*tem`po*ra"ne*ous*ly, adv. -- Ex*tem`po*ra"ne*ous*ness,n.
Wiktionary
extemporaneousness
n. The degree or property of being extemporaneous.