Hello Insiders! We have heard your feedback about supporting a dictionary feature to increase productivity while reading PDFs. We are excited to announce a new dictionary feature – our first step in the integration of smart actions in the Edge context menus.
The mini menu is an evolution of the context menu and allows quicker access to common browser actions and new smart actions like the define (dictionary) action. This new dictionary feature allows you to look up definitions of words while reading a PDF document in Microsoft Edge. This built-in dictionary is very easy to access and use. While reading a PDF file, simply select the word and a mini menu will appear near the word once it’s selected. You can invoke the definition card by clicking on the Define menu item. Alongside the definition, you can click the speaker button to hear the pronunciation. If you would like to search for more information about the word, you can click the 'Search for "selection"' to see more Bing powered web results in sidebar search. You can also access the dictionary feature in the right-click menu.
The dictionary feature is an addition to the mini menu for PDF annotations. In future edge versions, the on-selection menu and dictionary cards will also be supported on web pages in Microsoft Edge.
The dictionary feature is now available in Microsoft Edge Dev and Canary channels and supports these languages: German, French, Spanish, Italian, Russian, Portuguese, Swedish, Norwegian, and Polish.
Head to the ... menu in the top right of your browser window > Help and feedback > Send feedback to let us know how you like this feature or if you spot any issues!
Source: Introducing Dictionary for PDF mini menu