Composed,
performed, or
uttered on the
spur of the moment, or without previous
study;
unpremeditated;
offhand;
extempore;
extemporary
Example: "His speech was clearly entirely extemporanean. You could tell from the way he stuttered and how he paused halfway through his sentences sometimes, as if he were making it up as he went along. And he still beat me in the public debate. Pleh."