When you are reading a dense academic PDF, a complex legal document, or an advanced news article on your Mac, it is highly likely you will encounter a word you do not recognize. The traditional workflow is tedious: you highlight the word, copy it, open a new tab in Safari, navigate to Google, paste the word, and read the definition. macOS has a much better way. Apple has integrated the complete Oxford English Dictionary (and a full thesaurus) directly into the core operating system, allowing you to define any word instantly without ever leaving your document.
How to Use the Look Up Feature
This built-in dictionary works in almost every application on your Mac, including Safari, Mail, Pages, and Apple Books.
Method 1: The Trackpad Gesture
If you are using a MacBook or an external Magic Trackpad, you can trigger the dictionary with a single physical gesture.
- Move your mouse cursor so it is hovering directly over the unfamiliar word.
- Tap the trackpad simultaneously with three fingers. (Alternatively, if you have a modern Force Touch trackpad, firmly press down on the trackpad with one finger until you feel a secondary, deeper “click”).
A small, yellow, translucent window will immediately pop up directly above the word, displaying the full dictionary definition, the pronunciation guide, and a list of synonyms from the thesaurus. When you are done reading, just click anywhere else on the screen, and the window disappears.
Method 2: The Keyboard Shortcut
If you are using a traditional desktop mouse without a trackpad, the gesture will not work, but you can still access the dictionary.
- Move your mouse cursor so it is hovering over the word (or double-click the word to highlight it in blue).
- Press the keyboard combination: Control + Command (⌘) + D.
The exact same pop-up window will appear. If you want to configure which dictionaries the Mac searches (for example, adding a Spanish-to-English translation dictionary), you can type “Dictionary” into Spotlight Search, open the dedicated Dictionary app, and open its Preferences to download new language packs.