Improvise (verb)

1. Perform, speak, or compose without preparation.
2. Make or provide something using whatever is available.
3. Manage in an emergency without a pre-planned course of action.

Origin:

Mid 17th century: from french improviser or italian improvvisare, from in- "not" + provviso "foreseen".

Examples:

1. He improvised a song on the spot.
2. The actor had to improvise his lines due to a memory lapse.
3. The chef improvised a dish with the ingredients on hand.
4. The players had to improvise a plan when the coach got injured.
5. The soldiers had to improvise a shelter in the wilderness.