New York Times Dictionary Popup

Today I double clicked a word in a New York Times article to select it. I wanted to use my Mac’s built-in dictionary to look the word up. But to my surprise, a window popped open from the site with a dictionary definition and a thesaurus entry below. I clicked around on a bunch of other words and they all did the same thing. Very slick. It doesn’t appear to work on the main page, just on actual articles.