I'll guess that it's an astilbe.

I'd guess you've got Aruncus 'Horatio', which is a cross between A. aethusifolius and A. dioicus. The leaves are definitely from the aethusifolius, but the size sure isn't.

'Horatio' is described as being 80-120 cm tall; creamy-white, open, horizontal plumes; finely cut dark greem foliage.

Whatever it is, it's a beauty.

This plant just can't stay where it is. It must be moved. Should I attempt to do so this fall or wait until spring? Also can it take more shade? It is currently in an almost full sun situation.
Thanks Cailinriley for the identification. I googled 'Horatio' and I think you are correct.

Most perennials can be moved in late summer ... but, don't leave it too long, as they appreciate still having warm temps to reestablish themselves before freeze up ... otherwise, just wait till spring.

Yes, this plant will be happy with a less than full sun exposure, though I don't know about full shade?

Terry

I have one Aruncus planted in full shade. It does okay, but is much shorter than the label says, and still doesn't take up much room after several years. I think I need to move it closer to the front of the flower bed, so the height suits the location better, or else move it into a sunnier spot where it will (hopefully) get taller. I've had it for several years, so at least I know it's hardy for me in full shade.
Connie