WordWeb is a free English thesaurus dictionary and simplifies the process of searching meaning of a word.
You need to download it from its website http://wordweb.info/free/ and install in your computer. WordWeb is simple to use and what you need to do is just ctrl+right click on any word for which you want to know the meaning.
WordWeb displays the meaning for you in a small pop up box. This integration of thesaurus with local application makes WordWeb a winner.
Try this useful application.