The term "morph" is used to describe a form that is generally genetically stable, such as the blue morph of the Snow Goose. Your bird appears to be either partially albino or leucistic, two mechanisms that result in reduced or absent color.
Many years ago there was a white Red-tailed Hawk with just a red tail that overwintered for several years in PA. It had dark eyes so it wasn't an albino, or at least not a full one. If something like that shows up again now that I take photos, I'll be spending some serious time with it!