Just highlight the word and click the WordWeb icon in your system tray (or simply hold down Ctrl and right-click a word) to access a wealth of information that includes definition, synonyms, and spoken pronunciation--which requires sound, of course. Other results vary with the context but could include choices such as antonyms, types, and parts.
There's a dizzying array of options, including a choice of nine different types of English (for example, British English, Irish English, and American English).
Note: This trial version of WordWeb can be used for free indefinitely if you agree to strict air travel restrictions. The full version, WordWeb Pro, adds more definitions and numerous customization options.