How to Instantly Look Up and Define Words in macOS

When you are reading a dense academic PDF, a complex news article, or a novel in a foreign language on your Mac, you frequently encounter words you do not fully understand. Opening a new tab in Safari and typing the word into Google disrupts your reading flow and breaks your concentration. To solve this, Apple has integrated a lightning-fast, system-wide Dictionary tool directly into the core of macOS. It allows you to look up definitions, translations, and Wikipedia summaries instantly without ever leaving your document.

How to Use the Trackpad Shortcut

The absolute fastest way to look up a word is by using the Force Touch trackpad built into all modern MacBooks (or the external Apple Magic Trackpad).

1. Move your mouse pointer directly over the word you want to define.
2. Force click the word. (This means pressing down on the trackpad until you feel the normal “click,” and then pressing slightly harder until you feel a secondary, deeper “thump”).

A small, elegant pop-up bubble will instantly appear directly above the word, displaying its definition, pronunciation, and part of speech. If it is a well-known entity or location, it will pull in a summary from Wikipedia. To dismiss the bubble, simply click anywhere else on the screen.

Note: If you are using an older Mac without a Force Touch trackpad, or if you disabled the feature in settings, you can achieve the exact same result by tapping the word with three fingers simultaneously.

How to Use the Keyboard Shortcut

If you prefer using an external mouse or find the Force Touch gesture difficult to execute reliably, you can trigger the exact same pop-up dictionary using a dedicated keyboard shortcut.

1. Move your mouse pointer over the word (you do not need to click or highlight it).
2. Hold down the Control and Command keys simultaneously.
3. Press the D key.

The dictionary bubble will instantly appear over the word your mouse is hovering above.

How to Customize the Dictionary Sources

By default, macOS uses the Oxford American Dictionary. However, if you are learning a new language or prefer British English, you can customize the Dictionary app to pull definitions and translations from dozens of different international sources.

1. Open the Launchpad or use Spotlight Search (Command + Space) to open the Dictionary application.
2. In the menu bar at the top of the screen, click on Dictionary and select Settings… (or Preferences).
3. A window will appear listing every dictionary and translation database available on the operating system.
4. Check the box next to any source you want to activate (e.g., “Oxford Dictionary of English (British)” or “French-English translation”).
5. You can also click and drag the dictionaries in the list to prioritize them. The dictionary at the very top will be the first definition shown in your pop-up bubble.

Once activated, the system may briefly download a small database file in the background. Your trackpad and keyboard shortcuts will now instantly utilize your new, customized dictionaries.