In Pictures: 13 useful add-ons for Microsoft Excel...
Merriam-Webster Dictionary for Excel 2013 and Word 2013
Microsoft offers its own Bing-branded dictionary app for Office 2013, but an appealing alternative is by one of the respected names in the dictionary biz. With the official Merriam-Webster app installed, you can right-click on a word and choose “Define,” and a definition entry for it will appear in a panel to the right of the Excel 2013 or Word 2013 application window.
In Pictures: 13 useful add-ons for Microsoft Excel and Word 2013