I think Art is everything with Artistic Value for its beholder.
As what Artistic Value entails, it can range from enriching their mundane lives to changing it entirely. It is akin to how much color does one masterfully apply to a dull portrait that's the daily life of many.
That's speaking in general or as an object.
In my own definition of Art as an action, it's more like magical or supernatural powers. I want it to be stuff that makes what's usually impossible, into stuff that you can easily experience and gain lots of things from. Perhaps, if I were to put it in an outlandish term--like a gateway to Godhood.
You tried to be a God with your craft before you became one for real and actualize all your wishes into reality. Art is one of the learning tools for that. Whether you can fulfill it or not, it depends on your ability. Though the threshold might not be as high as it seem.
Though I do look forward to a world where dreams do come true. It's definitely one of the bigger reasons for people to do Art.