Very useful.
I like that I can see many things (synonyms, antonyms, definitions, etc.)
Only thing that could be improved is making it in such a way that you can move from one section to another just by scrolling on them (for eg. when viewing synonyms, be able to scroll down to the next section(s))
Also, on some websites, the icon won't appear for selected words, but IG this is the issue of the website.