Simple for me, I'll say that I've won the casino or I've beaten the casino when I made profit (overall) not only in a single gambling session.
Others may say they have beaten the casino when they can stop gambling in the casino once they made a profit and not coming back at all.
However, as long as we keep on playing on the casino while we are still making profit, it is actually we cant beat ourselves (our greed).
Greed is a side effect that can increase the level for everyone when they win too much and in the end don't think about a good exit strategy
and play all the winnings so that in the end they lose their profits and capital.
A full victory will not be possible if you are still tied to gambling and still make some deposits beyond the predetermined allocation,
this only delays the defeat, but if you are indeed aware that after a win there will definitely be a loss, you will secure that profit elsewhere.