done or said without earlier planning or preparation
See video “How to give an impromptu speech” in the Related Articles section below
Merriam-Webster Online Dictionary
impromptu (noun)1.
something that is impromptu
2.
a musical composition suggesting - improvisation
1.
made, done, or formed on or as if on the spur of the moment - improvised
2.
composed or uttered without previous preparation - extemporaneous
