There's no doubt that there is plenty of so-called HD content out there that isn't worthy of the name -- not to mention a broadcast radio technology that has nothing to do with definition at all -- but it seems that trying to comprise a specific definition of HD is simply an exercise in futility. This is because there are a few examples of HD that by any definition would be considered HD, but still look terrible. Just take some of the original movies released on Blu-ray for example or some of the less expensive 1080p HDTVs. Sure all the pixels are there, as well as the color space and frame rate, but that doesn't mean the encoder didn't go crazy and screw it up, or that the display can accurately display the colors or have a half way decent contrast ratio. So while it seems like a great idea to quantify HD, in practice, just let your eyes be the judge.