“Art is a human activity consisting in this, that one man consciously, by means of certain external signs, hands on to others feelings he has lived through, and that other people are infected by these feelings and also experience them.”— Tolstoy
If you ignore the parts about Christianity, Tolstoy’s definition of art is pretty sturdy. I don’t think that doing so undermines it, either. In fact, it’s been my personal litmus test for about fifteen years, and I can’t recall a time when it let me down. It’s broad enough to include most works of art I approve of, but (for the most part) excludes the ones I don’t.