I have a definition, which took me much more than two years to find. It all begins with the confusion between money and its representation, which I call "representational monetary identity." With commodity money, that confusion is already there from the beginning (it is not merely subjective), and usually evolves into the confusion between money and credit with a monetary proxy (gold-deposit receipts). With Bitcoin, the confusion between money and its representation requires a monetary proxy, which fortunately Bitcoin does not need. However, the difference between Bitcoin and commodity money goes far beyond Bitcoin having no need for a proxy representation: Bitcoin inherently distinguishes money (a private key) from its representation (a public key), a distinction its proxy representation would reduce to a mere possibility.