Bitcoin is not an asset, Bitcoin is money and the definition of money is a currency (ie. a medium of exchange) that can be used as store of value. This means because Bitcoin is acting as a store of value and also because it is in its early stages of adoption, its value keeps growing against fiat making it a suitable investment.
Calling Bitcoin an asset is like ignoring everything else that it offers which are far more useful.
I used my browser to search the meaning of Bitcoin, the response defined Bitcoin as a currency not an asset.
From my extended research, Bitcoin was created as a currency against fiat, the actual way to define Bitcoin is mainly a currency just like you did.
If Bitcoin is now used as a store of value, that means it also can serves as an asset, we can agree that Bitcoin is both definitions instead of taking away one.