a beauty quark is the second heaviest (thanks yossarian) of the six types of quarks, which are the building blocks of protons, neutrons and other exotic particles. Known previously as a bottom quark, prudish physicists decided to rename it. why? quarks are always found in nature in pairs or triplets, because the harder you try to pull quarks apart, the more force there is between the quarks, like a rubber band. if you pull hard enough to pull one quark away from the rest, you necessarily generate enough energy to create a new quark to pair with the one you were pulling on. So (as far as we know now) there is no such thing as a 'naked' quark -- a quark all by itself. in scientific literature, physicists would often mention 'naked bottoms'. i guess some physicists weren't appreciative of the joke, in any case they preferred 'naked beauty'.