Ultimate function

ENDUSE

Think of the final purpose or application something is designed for in two words.

"Ultimate function" hints at the final purpose or goal of something, which is often called its end use—the last step in a process. The answer plays on the phrase literally, combining "end" (meaning final) and "use" (meaning function) to form ENDUSE. It’s a straightforward definition with no hidden wordplay, just a direct way to describe the last intended application.