Here's my thoughts ...
"Grounded" and "resistant" seem to be terms that are taken various ways.
The "grounded" I'm working on is like this:
Instead of my body offering any resistance (remember Ueshiba's no resistance thing?) to someone trying to throw me, I have a pathway set up in my body that takes the incoming force and allows it to go to the ground -- no matter what position or placement my body is in. The person trying to throw feels like they are actually pushing the ground. No matter where I move or how I move, I have no internal resistance to the force coming in. It goes to ground.
"Grounded" to me does not mean "planted" or "immovable". Ever.
The "resistant" I'm working on is to not be easily thrown or my center captured. Even when I bring the ground back out and into the person, I am still not using resistance.
"Resistant" to me does not mean fighting or using muscle. On the flip side being "non resistant" does not mean tenkan out of the way of an attack.
I think this is a good, basic example of what it means to be "grounded" without being simply planted
Ignore the craptastic knife defense at the end though
2:09 has some good stuff in it as well