Well,...
> 1. A test under controlled conditions that is made to demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy of something previously untried.
That's the closest to my belief... as a believer in free will of living things, I believe that God created the initial conditions of the Universe, and the Rules (the laws of physics, etc.), but didn't pre-determine every event or outcome. In that sense, my concept of the "purpose" of the Universe could map loosely onto definition #1 of "experiment".
> A better term to use would be " God's purpose " ... God's plan, or divine will.
I have no issue or argument with that usage.
Incidentally, my view of "free will" does not in any way preclude seeking guidance through prayer, to better understand God's plan for the Universe and how I can best take part in it. At the end of the day, I still have a choice about what I do. But it's clear that some things work a heck of a lot better than others, and I generally interpret those outcomes as whether I'm following God's plan.