I started using it last year and I think others would benefit from knowing about it too.
Offline dictionaries(based on data from wikipedia, wiktionary etc.):
https://github.com/itkach/slob/wiki/Dictionaries
I use the Wordnet and SimpleWikipedia dictionaries along with the one for the Wiktionary in my native language.
Going on a tangent about the dictionaries(you can skip this if you’re currently not interested on that):
They had a Malayalam dictionary, which was quite awesome for me, as I’m a Malayali. The dictionary is based on ml.wiktionary.org from 2021. Maybe there were not too many additions for the effort to make a new one.
The code for creating the dictionaries are also available in their github. I tried it out, but I’m on Opensuse Leap currently and installing couchdb seems tricky.
I also saw a python package, Pyglossary, which helps to convert dictionaries between opensource formats.
Wikipedia provides monthly dumps of zim files(used in Kiwix, another dictionary app. Not available in F-droid).
https://dumps.wikimedia.org/other/kiwix/zim/
I was able to use Pyglossary to convert those into slob files and use them.
So might be an easier way to get slob files, if slob files of Wiktionary or Wikipedia in your language are not available. Or if you want to update them. Data scraping is also avoided.
How is this with Japanese because I’m currently learning it and would like to check this out
They have a Japanese wiktionary slob file. I don’t know Japanese, so not sure what the actual content is, but it seems to have definitions of both Japanese and English words in Japanese.