What is the word for using something for other than its intended purpose?

Ok, I found the answer: exaptation.

Using "improvise" and "improvisation" in a sentence to illustrate the meaning:

We lacked the purpose-built equipment to do the task, so we had to improvise, using only the tools available.

Our improvisation of using a garden hoe to mix the cement worked well.

@Argot -what's the answer to the title?

ad hoc
Latin, meaning: for this -Wiki

ad hoc can also mean makeshift solutions, shifting contexts to create new meanings, inadequate planning, or improvised events.

ad hoc \ˈad-ˈhäk, -ˈhōk; ˈäd-ˈhōk\ adjective -MW

1,b : formed or used for specific or immediate problems or needs
2: fashioned from whatever is immediately available: improvised