I am not sure if "money" is actually defined anywhere in U.S. law other than by giving examples, but "dollar" is certainly defined in U.S. law.

FRN's use the term "dollar" on them, yet since FRN's became no longer redeemable in gold, the Federal Reserve has zero connection to the public law definition of "dollar". The Federal Reserve is clearly operating under a different definition of the term "dollar" (private law or fiction of law definition).

This private law definition of "dollar" seems to be "one dollar United States note", since this seems to be all you are entitled to get from the Fed in exchange for a dollar FRN.

FRN's can no longer be redeemed for gold as of 1933, but the dollar itself continues to this day to be defined in public law as a given weight in gold. Therefore we have currency, we have lawful money, we have legal tender, we have notes, we even have coins, but none of them can be "dollars" according to the law of the land unless they are redeemable for a given weight of gold. Making it clear that Federal reserve Notes cannot possibly be lawful money according to public law.

The 1792 Coinage Act (amended in 1900 and still in effect today), states that a dollar is 25.8 grains or 1/20 of an oz of gold. The closest you could come to getting a dollar from Fed is to receive a U.S. Note, making it pretty clear that this is their private law definition of a "dollar".