PocketDict is a Freeware English Pocket Dictionary with for Windows Mobile based Pocket PC devices. It is based on OPTED, a public domain version of Webster’s 1913 Unabridged English dictionary with over 180 thousand entries.
Features include root-based and multi-thread searching, making it easier and faster to find words. Support for Cleartype, custom font size, allow you to customize your display, and a dictionary locator.
As a bonus, an online converted version of Microsoft Encarta is also available as an addon dictionary for PocketDict.

Download Links-
Pocket Dictionary 1.2 Setup (for ARM based processors only)- http://files.cellosoft.com/pocketpc/pocketdict/PocketDictv1.2Setup.exe
OPTED dictionary for PocketDict (8MB)- http://files.cellosoft.com/pocketpc/pocketdict/PocketDict-OPTED.zip
Encarta Dictionary for PocketDict (4mb)- http://www.cs.unm.edu/~cello/pocketdict/PocketDict-ENCARTA.zip