It's good sometimes, but more often than not it can't find a definition, which doesn't make it a particularly comprehensive dictionary. And if a word is a plural or any kind of variation, it can't find it either, just the simple form of the word, and there's no way to get a definition by highlighting a word without the 's' or whatever on the end, because you have to double click, which naturally highlights the entire word.
There's just too many words it can't find.

I really want to like this because when it works it works but it frequently just crashes and the pop up refuses to leave the screen

Incredibly inconsistent.

Works well, but has a thin vocabulary.

It only shows "No definition found" now

What happened? It used to work mostly fine. It does not recognize any word now

It takes long to search

the French dictionary is very incomplete. This makes this extension completely useless at least for this language

good idea, but uncommon words are not often defined (you know, the sort of words you need a dictionary for)

Mostly works but there are problems with it that make it just barely okay. First, double clicking a word in an edit field brings up the definition. That shouldn't happen or there should be an option to disable it. If I double click a word in a text area, I don't want its definition, I want to do something with it, maybe style it or replace it with something else, but this extension often makes that difficult. Then the popup. It's sometimes slow but worse is that if the text I double click is on the right side of the screen, the popup bubble doesn't change direction and it partially appears outside the screen.

Wanted context-menu definition, but instead it pops up on EVERY double-click, which is annoying.