Is being a "pronator" the same as having flat feet?

It’s when your ankles turn inwards. It’s a side effect of flat-footedness.
You are going to want the sturdiest arch support that you can find. You might even consider purchasing orthotic shoe inserts. The resin ones hold up for a long time – mine are nearly ten years old.

No. Flat feet is described as when the arches of your foot have completely collasped, and your whole sole of your foot touches the floor. Pronation happens when you are standing and there is more pressure on the medial side than the lateral. A person can still have arches in their feet and be a pronator. I am. If you go to a good running shoe store they may have one of those machines that measures the amount of pressure in your feet, in order to supply you with proper arch supports. You can wear them in any style of shoe.

It is not about flat feet.
Here is a good description

See your Podiatrist. They can also help you with what to look for and what you may need if you are going to run and have certain conditions.

“Overpronation
As with the “normal pronation” sequence, the outside of the heel makes the initial ground contact. However, the foot rolls inward more than the ideal fifteen percent, which is called “overpronation.” This means the foot and ankle have problems stabilizing the body, and shock isn’t absorbed as efficiently. At the end of the gait cycle, the front of the foot pushes off the ground using mainly the big toe and second toe, which then must do all the work. ”

Runner’s World

Thanks, everybody, for your answers. Special thanks to @blueiiznh and @marinelife for the links!

I have congenital flat feet, and I discovered that not only are my ankles involved, but the knees also. One of my knees turns inward, which contributed to a problem I had with skiing. It wasn’t until after I got my ski boots canted that I was able to successfully ski in powder. Interesting that the podiatrist and sports medicine doctors missed that.

Once your arches are flat, you will harm yourself to try to make them go back by wearing an arch support higher than your foot will tolerate. I did this, not realizing that the shoe I had bought had too high an arch, and nearly crippled myself for a while. What you want is to support the arch you have left. In my case I’m very happy with one from Profoot that is designed for people with flat feet and it molds to the shape of my foot. I also cannot wear high heels safely or comfortably.

If you do buy an arch support, make sure you remove the one that came with the shoe you want to wear. Some shoes have a built in arch support which cannot be removed, so be careful what you buy. I don’t know about running shoes, but you might see if you can find one that will allow you to put in your own arch support. If so, be sure to try it on with the new one inside before you buy.