Now you have my attention, #CLMoocers! I know this one!
As Wittgenstein shows us in Philosophical Investigations, although it is tempting to assume that all games must have something in common, that’s not the case:
For if you look at them you will not see something that is common to all, but similarities, relationships, and a whole series of them at that. To repeat: don’t think, but look! (Section 66)
Quite. There is no essence of gaminess that all games share. You can give a narrow definition of certain type of games, but this definition will likely not apply to other games.
Look for example at board-games, with their multifarious relationships. Now pass to card-games; here you find many correspondences with the first group, but many common features drop out, and others appear. When we pass next to ballgames, much that is common is retained, but much is lost.—Are they all ‘amusing’? Compare chess with noughts and crosses. Or is there always winning and losing, or competition between players? Think of patience. In ball games there is winning and losing; but when a child throws his ball at the wall and catches it again, this feature has disappeared. Look at the parts played by skill and luck; and at the difference between skill in chess and skill in tennis. Think now of games like ring-a ring-a-roses; here is the element of amusement, but how many other characteristic features have disappeared! And we can go through the many, many other groups of games in the same way; can see how similarities crop up and disappear. (Section 66 cont.)
So, by my reckoning, if you think it’s a game, it’s a game. Apply the Duck Test and, as Douglas Adams said:
If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family Anatidae on our hands.
Simples. Unless anyone can persuade me otherwise.