A 'Fiat' currency is one which the government of a country has declared to be the official currency...by government fiat.
That does not include Bitcoin.
Gold is not a distributed fiat currency. It is just Gold. You can exchange gold for currency, or you can make payments directly with it, if the person is willing to receive them.
"A 'Fiat' currency is one which the government of a country has declared to be the official currency...by government fiat."
No, it is not. You are falling prey to a rather politicized definition of the term. All non-commodity currencies are fiat money, but not all fiat currencies are backed by a government.
The word "fiat" is Latin for "let it be done" or "it shall be". It implies only that something happens by decree. The party making the decree does not have to be a government, or even a person of authority.
That does not include Bitcoin.
Gold is not a distributed fiat currency. It is just Gold. You can exchange gold for currency, or you can make payments directly with it, if the person is willing to receive them.