I am going to save myself some typing by copying and pasting the 3-star review by active x:

"Great! It just works. However, I had to uninstall it because the 'double-click to lookup' feature cannot be disabled. I don't like it that it immediately works on my selected text when I would often be just double-clicking to select text to copy it.

"There's another extension named 'TheFreeDictionary.com Lookup' that works just like that. I was hoping to use the official one for being more trustworthy."

I agree, word for word, including recommending that other extension. Why? Because that one works just as well but allows one to use the right-click context menu instead.

Very short-sighted of Farlex to assume that one would only double-click a word or phrase on a web page for the purpose of looking it up on TFD. And, I mean every time, no exceptions, no options. This would have driven me nuts.

I am not as charitable as active x, however. Only two stars from me; it would have been one if I did not value TFD as highly as I do otherwise.