1. To give an unplanned or unrehearsed performance; to act, sing, speak, or perform without preparation
The musician decided to perform impromptu at the street corner.
O músico decidiu fazer uma apresentação improvisada na esquina da rua.
2. To spontaneously engage in a performance without prior arrangement or script
She performed impromptu poetry for the surprised audience.
Ela recitou poesia improvisada para o público surpreso.