Currency. Coined money and such banknotes and other paper money as are authorized by law and do in fact circulate from hand to hand as the medium of exchange. (citations omitted.) -- Blacks Revised Fourth
It continues:
The term "money" is synonymous with "currency," and imports any currency, token, bank notes, and other circulating medium in general use as the representative of value. (citations omitted)
These citations are misleading unless you read them correctly. Currency is not just the same word as money. They are different concepts that just happen to often overlap. Currencies have historically been comprised of legal money because banks and governments have historically been reliable guarantors of future value. But there is no reason money must be backed by government force. And there is no reason that currency must be money. Anything that circulates as a medium of exchange has currency. Period.
Money may be currency, if it is readily exchanged. And currency may be money, if it has future value, either innate or by fiat. Currency, however, is not necessarily money and money is not necessarily currency. Over the last decade, for instance, gold and silver have been much better monies than Federal Reserve Notes. Yet gold and silver are not currencies since they can't be used to purchase a hamburger.
Don't argue with me. Argue with the guy in the black robe.
There's no reason to argue with anyone in black robes. Since the US is a common law jurisdiction,
All it takes is a rational survey of the terminology and issues, and an agreement on which terms are proper to describe Bitcoin.
Which we have done already. Bitcoin is a currency, since its function is to circulate as a medium of exchange, and since it in fact does so. But you can call it whatever you'd like.