A fiat currency is like the US dollar or Euro, a backed governmental currency based on a commodity backing like oil , gas, natural reserves, industrial merchandise ect, take the US fiat currency..In the old days it was pegged to gold and silver you could actually take a 20 dollar fiat bill to a bank and get the equivalent in gold given to you. That regulated the money supply to the amount of gold the country had which was not as fast in creating wealth as they wanted so they unpegged it from gold and allowed banks to loan however much they wanted to. today i think they can loan out 9 dollars to ever 1 dollar they have. When they unpegged from gold they used commodities or any hard asset be it oil or corn.

Steem and SBD is not until converted to a above fiat currency.

The form of currency Steemit uses or process is that crypto has to be purchased or given to someone bought with a fiat currency. Then the crypto can be used within the system. In order to have value it in turn has to be exchanged again for fiat currency

All crypto is a decentralized, self-governed environment but has no value unless converted to a gov commodity backed Gov currency like USD or Euro.

You can call any crypto a fiat currency the point is its not backed by a commodity so has no value until exchanged through a fiat backed by a Gov.

Example would you take 5000 usd in crypto for your car knowing you could not exchange that crypto for a a fiat currency backed by a Gov USD or Euro ect. If you do then its called a bartering system. And you would only be able to use the crypto you have to purchase something someone else has to sell that does not want hard currency as in usd or euro and will take only crypto.