how can I enable in Preview.app the three fingers gesture that shows the selected word in the dictionary?

This gesture works great in Mail.app but doesn't in Preview.app

  • Strange enough, even the shortcut for it does not work.
    – Ivan Xiao
    Sep 12, 2011 at 15:45

1 Answer 1


Are you viewing a PDF? Unfortunately, the three finger tap gesture does not work with PDF files across the system (e.g. not in Safari as well).

The most convenient alternative I can think of is double tapping a word to select it and then two-finger tapping on that word to show the context menu in which you find the command "Look up word in dictionary".

  • 1
    May I ask how you know it does not work with PDF? Is it said in the official document? I checked and seems true. But I just cannot imagine why it does not work, since literally you have the "Look up word" option.
    – Ivan Xiao
    Sep 12, 2011 at 15:45
  • It's just a guess from my side, judging from the behavior I observed. And with the technical background knowledge that different programming elements are used in OS X to display normal, editable text and to display PDFs. My guess is that it wasn't deemed important to make the latter behave as the former in that respect.
    – mss
    Oct 7, 2011 at 20:17
  • Okay, after some observation I found that sometimes it works while sometimes not. Have no idea what is going on.
    – Ivan Xiao
    Mar 6, 2012 at 3:30
  • I don't really think so. I remember before updating to the new macOS version the three-finger gesture in Preview works just fine, it was so convenient for me to look up words quickly when I read documents. Now it just won't work anymore I'm really fed up.
    – Gerry
    Apr 21, 2017 at 11:06

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