Pop-Up Dictionary от R Leung

This extension makes use of on-line dictionary sites to translate selected words on-the-fly on a pop-up box.
It supports the following functions:
- Multiple dictionary sites can be defined
- Users can define custom dictionary sites (just input the url of the dictionary sites as "http://www.your-favourite-dict-site.com/$$". The $$ is a place-holder for the word to be translated.
- This extension will log the dictionary chosen for a particular web page you visited. The next time you visit the same web page it will know what dictionary should be used for this site.

How to add a new dictionary:
https://youtu.be/JDCCVYuLLFM