New test feature: Word Wise for EPUB books. It can be downloaded from GitHub Actions.
I use the Wiktionary data from
https://kaikki.org, the English JSON file is 1.4GB, other language files should be smaller then that.
I only enabled this feature for the 21 languages that have the spaCy model, but this feature could work for any language as long as it's on Wiktionary and kaikki.org
Some definitions may be incorrect, you could fix them manually in the customize wiktionary dialog.