Above all, the definition of money itself still considers it as anything that is an asset and exchangeable for its worth. Since Bitcoin is an asset and is exchangeable for its worth, it's money in my conclusive view. But for it to be thoroughly fitting, I guess that there should be some kind of modification to the definition of money. They never considered an advanced situation like we now see in cryptocurrency when they actually tabled down the definition of money.
The issue with the definition of money is that there are other characteristics which are supposed to be held by an assets to be considered to be money, not only the fact there is an existing and big liquidity for that asset. Otherwise, we could argue gold is money, because of its high liquidity and market. Account the the most conservative definition, for an asset to be money it would need to keep it's relative value through time, be accepted as unit of account and accepted for the exchange of good and services.
In the case of Bitcoin, it lacks the capability to keep it's value stable through time, hence why is a very good vehicle for speculation.
So, I could easily argue Bitcoin (as stands today) behaves more like an asset or commodity than actual money.
Though, volatility is not an imposible obstacle to avoid if a jurisdiction actually wants or desires to use Satoshis as a official currency. El Salvador is an example of it being possible.
All the problem with casinos and Bitcoin as money actually comes for the digital and decentralized properties of the Blockchain, which the governments and the authoritarian ones are scare of, thrus they need to push as much regulation as possible to slow down money laundering and other criminal activities, in detriment of the positive experience of legitimate gamblers who just want to have fun and try their luck.