Although this is non-technical, generalised descript, here is a definition of a planet from dictionary.com:
"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."
Personally I think we should keep Pluto as a planet, and also classify UB313 as a planet as well. But then again what do I know?
