A: Firstly, I think it's important to ask the question, "how do you define art?", rather than "what is art?", since this is inevitably one of those subjects on which everyone will never agree. And so this is not my attempt to define art so much as an explanation of what I personally consider to be art.
True to my diplomatic nature, I take a rather subjective and radically inclusive approach towards art, that is inspired by the archetypal eighth grade literature teacher's philosophy on wrong answers: the only wrong answer is the one which you are incapable of defending. And so, if somebody - anybody - can make an argument that a certain thing is art, then I am willing to concede that it is art.
The reason I'm willing to do this is because, though art is a form of object, it is not the "thing" of art, but the "effect" it has on the human heart (whether that of the artist or the audience) that matters. Thus I believe that art can indeed be accidental, and both intent and interpretation can create art, not always in the same object.
To be (only slightly) more concrete, I support the theory that art is a [man-made] reflection of life, and the universe that surrounds us. It is an expression of existence as interpreted through human being. It makes some kind of statement (whether consciously or not) about - or it expresses a reaction to - being, as experienced by a conscious intelligence.
None of this makes any distinction between good art and bad art, nor between "high" art (i.e., fine art) and "low" art (i.e., pop art), which are independent scales that are themselves subject to a considerable amount of subjective interpretation. These are all just different kinds of art. But they are all art, and the important thing about art is that it comes from human hands (even as it sometimes reflects the world beyond people), and that it touches the human heart.