After a whole day of struggles, I finally managed to convert a wordnet3 infused dictionary (that you can get here: http://eb.lv/) from .mobi format to .dict format (suitable for KOReader).
I tested this process on Arch Linux, so your process might be different from mine.
- Download the KindleUnpack program from here: https://github.com/kevinhendricks/KindleUnpack
- Extract the .zip
- Start the GUI with python 2 (IMPORTANT: python3 doesn't work!):
python2 KindleUnpack.pyw
- Select the .mobi file as input and choose your output directory
- (optional) I don't know if it is necessary, but select ePub Output type: Auto-Detect