I prefer a definition synthesized from those proposed by Stern & Levinson, Buie, Basri, and Brown. That is:
planet: an object that orbits a star or stars and is large enough to be shaped primarily by gravity ("rounded") but not large enough to have ever undergone fusion in its interior
A planet that can dynamically clear its orbit--that is not part of a population, belt, or cloud--is a "major planet," while a planet that cannot clear its orbit is a "minor planet." There are 8 major planets in the solar system, and an unknown number of minor planets, of which Pluto is the most notorious. The four largest asteroids are also minor planets, as are all of the big KBOs and Sedna. The 8 major planets plus Pluto comprise the "historical planets," freeing anybody from fretting about Pluto's classification. It is always a planet, but its significance depends entirely on what you're talking about.
Objects which meet the mass requirements but to not orbit stars are simply "planetary bodies." A planetary body that orbits another planet is a "planetary-scale satellite." A planetary body that does not orbit a star or planet is an "unbound planet."
For comparison, Stern & Levinson use the same definition, but call major planets "??berplanets" and minor planets "unterplanets," which strike me as unneccessary neologisms. Basri calls spherical non-fusing bodies "planemos" (
planetary
mass
objects) with planemos that orbit stars known as planets. Again, I don't see the need for new words. Buie uses the gravity-fusion definition without caring if a planet orbits another planet, so all the big moons are planets, too. Brown used the "not part of a population" argument alone, disregarding mass--though he seems to have abandoned that idea by suggesting 2003 UB313 is the tenth planet.
I blended all those together into one that made the most sense to me. Just thought I'd share.
