Take note that this article (like all articles in this chapter) was translated from Russian cine reference book published in 1965. So, we are talking about film only.
Resolution is ability of the lens to register tiny details separately. The resolution is measured in lines per mm that can be distinguished on the negative film. This resolution definition ties a lens properties with some film quality parameters, so it describes rather not the lens alone, but the lens/film system.
Resolution is measured by shooting of transparent test charts with test images in center and at frame field. Special camera is used to provide perfect image plane.
Resolution values in reference books are provided for a fully opened relative aperture of the lens.
Resolution value drops toward image border usually, that is why it is usually provided for center and for edge (or border). When you stepping the lens down, resolution grows initially to some extent, but then it may drop again.