Art?

So I'm sitting in Hastings (Barnes & Noble being too far to walk to) and looking at art books. And it comes to me. I don't know what I'm looking for. Not in the sense of not knowing which artist or style I want to see, but in the sense of being completely lost. Sort of like those dreams where you can fly, only forget how when you're a hundred feet up. That same stomach-clenching sense of WTF?!

Now as I sit here, I'm still at a loss. Let's see what Oxford has to say about it.

art¹

• noun 1 the expression of creative skill through a visual medium such as painting or sculpture. 2 the product of such a process; paintings, drawings, and sculpture collectively. 3 (the arts) the various branches of creative activity, such as painting, music, and drama. 4 (arts) subjects of study primarily concerned with human culture (as contrasted with scientific or technical subjects). 5 a skill: the art of conversation.

— ORIGIN Latin ars.

Hmmmm. Not very helpful. That covers everything from oil painting to graffiti. How, then, do we differentiate between the Mona Lisa and Kilroy Was Here? The technical quality of the work? That would leave a lot of modern art out of the equation (not a big loss, to my way of thinking) and include a lot of things not normally considered art (comic books, anime, video games). The subject matter? (Personally, I'd prefer to look at weird monsters and giant robots than to stare at a bowl of fruit or some blotches of color.) Maybe the emotional response from the viewer? (Seems like porn would win hands-down in that case...:P)

My understanding still seems incomplete to me. I suppose I'll have to actually take an art appreciation class some time.