The Free Dictionary

http://www.thefreedictionary.com

TheFreeDictionary.com has a friendly Web2.0 user interface. Apart from providing convenient access to word look ups on Dictionary/ Thesaurus, Computing Dictionary, Medical Dictionary, Legal Dictionary, Financial Dictionary, Acronyms, Idioms, Columbia Encyclopedia and Wikipedia, TheFreeDictionary provides free voice pronunciation of the words that you are are looking up. Furthermore, the cross reference to Classic Literature portion provides a very good access to understanding how the word is being used in different context.

You can also download a free browser add-on from TheFreeDictionary. The Desktop Assistant has been developed by Sphinx Software. This convenient software allows you to access The Free Dictionary's definitions and encyclopedia entries by selecting a word or phrase with one click. It works in almost any application.