Sedna should be the 10th planet by that definition. But I bet there are alot of KBOs that satisfy the criteria too, all the way out to 250,000 AU, or half-way to Alpha Centauri. Probably thousands of 'em.

Assuming there is probably infinite variety, I use three fundamental categories if really pressed for definitions:

1. Gas giants.
2. Lifeless rocks.
3. Earth or Earth-like.

This has been a little messed up with the discovery of "exoplanets". We call *them* planets just because they are large enough to be discovered first. This is how it all got started in our own solar system. I say nip it in the bud before we have a galactic crisis on our hands!