"Planet" in my book is anything that's too big to just be a large lumpy rock. Something with sufficient gravity to pull itself into the shape of a sphere.

The idea of planets needing to orbit in eliptical orbits on a plane, or clear their own paths is a bias from living in a stable planetary system, but much of the planetary systems and indeed much of the universe doesn't have the stability that exists in this local area, it's especially the case in younger planetary systems as well as much older ones.

Also many planets in the universe don't even have stars, they are rogue, scattered throughout the darkness between the stars.