impromptu
im-promp-tu
adverb
Without preparation; spontaneously.
"He spoke impromptu at the event."
adjective
Done or said without prior preparation or planning.
"The impromptu speech surprised everyone."
noun
An unplanned performance, speech, or musical composition.
"She played a brilliant impromptu."
Thesaurus
Synonyms: ad lib, ad libitum, spontaneously, extempore, offhanded, unprepared, unrehearsed, extemporaneous, offhand, ad-lib, off-the-cuff, extemporary