Yes as long you use a thing to pay it is called money, so Bitcoin and other cryptocurrecy is a money that thing that it is different with the fiat is it's appearance because bitcoin is a digital currency. So bitcoin is a money and the other alt coin too.
Bitcoin is money but its not an altcoin for sure in fact its an foundation of other altcoins as you cannot use any altcoin for buying or getting fiat in hands and if you have to do then first you need to sell your altcoin to bitcoin and then can get fiat currency.