What is a planet?

What IS the definition of a planet? I had never thought about it until I read this article.

For example, I had started of this post with "planet : has a core, yes?" then had to stop and think. Core? What core? Our planet - there's that word again - has a supposedly molten core. Or a hollowed out one. Depending on which school of thought you're from. But then I thought..... isn't Jupitor a planet too? But that's a gas giant, yes? Aw shit, am I having a blond moment?

I turned to Wikipedia.

"Much like "continent", "planet" is a word without a precise definition, with history and culture playing as much of a role as geology and astrophysics. Recent definitions have been vague and imprecise; The American Heritage Dictionary, for instance, formerly defined a planet as: A nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves. In the solar system there are nine known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, Neptune, and Pluto. However, for some time that definition has been viewed by many as inadequate. The eight largest planets (which are also the eight nearest to the Sun) are universally recognised as such, but there is controversy over Pluto and other objects rounded by their own gravity. For this reason these eight are often universally referred to by astronomers as "major planets"."

ahHA! I'm not alone! No blond moment, thank god.