If you’re looking for a dictionary application made by Microsoft, the new Bing Dictionary is available to download for free in the Windows Phone Marketplace.
There are lots of useful features included, like the ability to use a local dictionary which contains 100,000 most-frequently-used English and Chinese words; you can always go online and use the dictionary there for more words, sentences as well as voice. The fact that it also supports Chinese will help Microsoft start its push in the market once Windows Phones — aside from the HTC Triumph — become available.
Notable features also include Smart Index which matches incomplete words and their inflections, search suggestions, machine translation supported by the online dictionary, several themes and fonts as well as search history. Follow the source link to grab it.