Did you know you can instantly access a dictionary, thesaurus, or Wikipedia entry for a word or phrase, from nearly anywhere in Mac OS X? All you need to do is remember a super easy three-finger tap trick.

How to Use Tap to Define Words on the Mac

Here’s how the three-fingered tap-to-define trick works on Mac OS X, which may be familiar to users on the iOS platform:

Hover the mouse cursor over a word (or select a word or phrase with the cursor)

Apply a three-finger tap (not a click, just a tap) onto the trackpad while the cursor is hovered over the selected word

You’ll instantly see the dictionary, thesaurus, and Wikipedia entry for the selected item, if it exists of cousre.

Applying a three-fingered tap on any word in a modern Mac app brings up this handy pop-up dictionary, thesaurus, Wikipedia summary. If the summary isn’t enough information, you can select to read more directly from the QuickLook-esque popup.

This is a students dream, but it should be useful to anyone reading things on the web or elsewhere when they run into a word they want some more information on, whether it be just a simple definition or the entire Wikipedia backed entry on a topic.

Encyclopedic pop-ups appear to work on any Mac with a multitouch trackpad and in all native OS X Cocoa apps – Safari, TextEdit, Pages, etc – it’s an OS-level feature that developers can include in their apps too.

This feature is included in all versions of OS X after first being introduced with the release of Mac OS X 10.7 Lion some time ago, but you’ll find the same abilities, with further enhancements even, through OS X Mountain Lion 10.8, OS X Mavericks 10.9, OS X Yosemite 10.10, and beyond.

If you don’t have this feature available, be sure you try in a supported application (most are these days), and be sure that you’re running a modern version of Mac OS X software. You’ll also obviously need a trackpad or a touchpad surface, like a Magic Mouse or Magic Trackpad, if not a Mac laptop, to have the touch feature available. As mentioned already, iOS devices have a similar tap-to-define feature, which is really handy for iPhone and iPad as well.