Definitions - a whole new ball game, so to speak. Does a "sport" require a specific amount of physical exertion (bowls)? Why not mountaineers, anglers? It needn't be outdoors (gymnastics) but I believe the winner should be measurable - fastest, strongest, etc - and not subject to the vagaries of judges. Gymnastics, ice dancing, diving and synchronised swimming are graceful art forms. But why not have Olympics for music hall acts such as acrobats? The established sports will remain sports forever, commercial interests will guarantee that, but IMO snooker is a sport too.
(Whether the Crucible winner is really a "world" champion is a different matter, when it is largely a Commonwealth sport. Rather like "world" champions at American football (which I also like) are ... well, American! But bear in mind, on that point of restrictions, that the world light-heavyweight champ - even if it's a unified crown, and it seldom is - is only the best among those boxers of a certain weight range.)