1. to speak, perform, or produce something without prior preparation or planning
The jazz musician had to extemporize when the original composition was lost.
O músico de jazz teve que improvisar quando a composição original se perdeu.
2. to compose, recite, or perform something on the spot with little or no preparation
She extemporized a speech after the microphone malfunctioned.
Ela improvisou um discurso depois que o microfone deixou de funcionar.