> According to this definition, is there any possible form of widely-used money that isn’t fiat money?

There used to be 100+ years ago such as gold and silver coins where if you were able to remove them from Country A to Country B, then Country A could no longer enforce such financial penalties against you. This is what many of the cryptocoins _wanted_ to be.

It needs to be a hard currency that leaves you immune to monetary policy and fines unless you are physically within the jurisdiction of the country.