Hint: Bitcoin has no intrinsic value, nor is it fixed to any objective standard => it is fiat currency by almost all useful definitions of the word fiat, sorry
Alright bud, listen. I picked that definition from dictionary.com (you call it "a place?") to provide the definition of that term. This definition is wholly relevant to its usage in monetary economics, as a "fiat currency" is a currency "by decree" of a ruler or government.
We could go to another "place" and get another definition, this time of "fiat money," specifically. The first line from Wikipedia: "Fiat money is money that has value only because of government regulation or law."
Given these two definitions provided, we can observe your statement, "bitcoin is a fiat currency by almost all useful definitions of the word fiat" and it becomes apparent that you don't quite know of what you speak. Bitcoin is in no way a fiat currency. It is not created by any government. Its value does not come from a mandate for usage.
And on "intrinsic value"... nothing has intrinsic value, for that would mean the thing has value without a human to value it. Things have value to the extent they are useful to humans and scarce. Bitcoin is both absurdly useful and limited in quantity, thus it commands a market price. You don't have to agree with the price, but at least try to make sure your statements regarding fiat money and value are valid.