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".

Works perfectly .

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.

Looks nice but unfortunately it's US Americanized English only.

No definition found almost every word.

Perfect ADD-ONS. Exactly What i was looking for.

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".

Just installed, works really smoothly by opening an overlay when a word is selected, and contains a brief explanation of the word (tried with English text). This is exactly what I needed. Kudos to the developers.

Great, simpledictionary (though would really love more languages added, like Arabic). Besides the language limitations, my only quibble is one that has been mentioned: popups shouldn't occur in edit fields. Double clicking on a word to retype it brings up the popup and obscures the text.