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.

It sweeps me away from the page I am looking up the word in question. It could be a pop-up just above or beneath the word.