Definition of "diagrammatic"

Moreover, a diagrammatic map of the electrified area is repeated at the top of every page.

1960 December, “The Glasgow Suburban Electrification is opened”, in Trains Illustrated, page 714

He sits facing a diagrammatic wall map of the area under his supervision.

1962 May, G. Freeman Allen, “Traffic control on the Great Northern Line”, in Modern Railways, page 341

What we need is some way of representing all this information about constituent structure in diagrammatic form. In fact, this can be done in terms of a tree diagram [...]

1988, Andrew Radford, Transformational grammar: a first course, Cambridge, UK: Cambridge University Press, page 51