Kevin Chau's German Dictionary

This project builds a bilingual German-English and English-German dictionary for macOS's built-in Dictionary application.

To build:

cd dictionary
make all install

This should convert the dictionary entries defined in the XML file into an Apple dictionary format, and then place it in the ~/Library/Dictionaries folder.

All you have to do after that is open Dictionary.app, go to menu Dictionary > Settings or shortcut cmd + ,, then check the box for Kevin Chau's German-English Dictionary.

You'll need to restart Dictionary.app every time you rebuild the dictionary, but you do not need to re-add the dictionary.

https://developer.apple.com/library/archive/documentation/UserExperience/Conceptual/DictionaryServicesProgGuide/Introduction/Introduction.html