to make or provide (something) using what is available
We improvised a stretcher from branches and a jacket
to compose or perform (music, poetry, drama, etc) impromptu or without a set script or musical score
improvisation /-ʹzaysh(ə)n/ noun
improvisational adj
improvisatory /-ʹzayt(ə)ri, -ʹviezət(ə)ri/ adj
improviser noun
[French improviser from Italian improvvisare, from improvviso sudden, from Latin improvisus unforeseen, from in-1 + provisus, past part. of providēre: see provide]