Extemporiness :: Extemporiness (n.) The quality of being done or devised extempor.
Extemporization :: Extemporization (n.) The act of extemporizing; the act of doing anything extempore.
Extemporize :: Extemporize (v. i.) To speak extempore; especially, to discourse without special preparation; to make an offhand address..
Extemporize :: Extemporize (v. t.) To do, make, or utter extempore or off-hand; to prepare in great haste, under urgent necessity, or with scanty or unsuitable materials; as, to extemporize a dinner, a costume, etc..