Retrofit is a verb that means to adapt to a new purpose.

The prefix retro, from the Latin word meaning ‘back,’ is used to indicate something that takes us back in some sense. In the case of retrofit, we are describing going back and altering an item to meet needs that have changed.

When I needed a backpack for the hiking trip, I had to retrofit my banjo case to carry food in it. It was surprisingly easy to adapt the case for his new purpose.