im·promp·tu (ĭm-prŏmpt, -ty)
1. Prompted by the occasion rather than being planned in advance: an impromptu party.
2. Spoken, performed, done, or composed with little or no preparation; extemporaneous: a few impromptu remarks.
With little or no preparation; extemporaneously.
1. Something, such as a speech, that is made or done extemporaneously.
2. Music A short composition, especially for the piano, performed in an offhand or extemporized style.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.