Doesn't work.

useless! About 1 in 50 words get a definition.

Doesn't even work.

Majority of the definitions I selected on a webpage comes back with "no definition found", and I am talking about the simplest words like "asinine" and "relationship".

There used to be Dictionary Search add-on with many configurable URLs. It is now gone, and instead we have this piece of crap with the single URL that opens a new window. Utter joke.

No definition found almost every word.

Majority of the definitions I selected on a webpage comes back with "no definition found", and I am talking about the simplest words like "asinine" and "relationship".

Continuously get the "no definition found", tried turning off all my other extensions but that wasn't it, seems to be a problem wit the extension itself? Reinstalling did not work.

My language is set to (US) English. I click a few words on a French page.
'propres' brings up a French definition, not an English translation 'propre: Qui appartient d'une manière exclusive ou particulière à une personne, une chose.'
Double-clicking 'permet' displays 'permit: Give authorization or consent to (someone) to do something.'
'invitent' gives 'No definition found'
'nombre' results in a Spanish definition, 'nombre:
Palabra o conjunto de palabras con las que se designan y se distinguen los seres vivos y los objetos físicos o abstractos.'

Update: the extension stopped working lately. Sucks.
-
Simple to use and it works. Double click on a word and you get a definition.