Improvisation (noun)

1. The act of making something up as one goes along, without prior preparation or planning.
2. The art of performing without a script or plan, using spontaneous creation and imagination.
3. Something created or done without prior preparation or planning.

Origin:

Late 19th century, from french improvisation, from improviser "to compose or perform extemporaneously", from italian improvvisare "to compose or perform without preparation", based on provviso "unforeseen".

Examples:

1. The actor's improvisation skills were put to the test when he had to ad-lib a scene.
2. The jazz performance was a demonstration of masterful improvisation.
3. The chef's improvisation with the ingredients produced a delicious meal.
4. The children's play was an improvisation based on their imagination.
5. The response to the crisis required quick thinking and improvisation.