Impromptu or Improvosation is the answer
careless or carelessly; impulsive; mechanical
They are a lot of controversy going on with the word publicly and publically. People do not know how to use the word, but it should be publicly, as publically is not a word.
Something that is done suddenly without any prior preparation.
The word publicly is an adverb (openly).
I have a tenancy to speak without thinking first
He publicly apologized for embarassing her. The opposition was publicly recognized for having run a fair campaign.
Synonyms for "preparation" : readiness, alertness, groundwork.
The correct term is "ad lib." It is a word which refers to something that is spoken without preparation. A good synonym for the word is improvisation.
She was publicly embarrassed when she ran into the stop sign at the busy intersection.