Well, the definition varies. At my company, it's a collared shirt and slacks or khakis for men, and socks and shoes. For women, it's slacks or skirt, a collared shirt or blouse, or sweater or cardigan/twin set, hose with closed shoes. (ie no open toes, no open backed shoes). A polo shirt for men is pretty borderline.
Now, I would surmise that the Disney version is not quite that strict.... We usually wear a combination of the above at CG, but I certainly don't wear hose or closed shoes.
Having said that, I have seen a wide variety of attire there....