Westphalian borders in the sense of the Westphalian states. Aka, each of the countries ends at a defined and demarcated line instead of areas of influences. You could think of it as “modern borders”. I don’t know if the term is also used in English, but last time I posted it (on Reddit) nobody questioned it, asked about that part, I learnt it at the university in my geography course.

I used to makes a lot of maps like this or using a GIS of variable quality, interest and end result. Also, I didn’t check if I made some spelling / grammatical mistakes back then on this one, but since the word count is low it should be fine, even if I messed up with fewer.