Windows Mobile users can download free Dictionaries for Windows Mobile phone.
1. Pocket Dictionary 2.5 is a free Dictionary for Windows Mobile containing 20 dictionaries with more than 2.5Million words.
Download : http://www.free-soft.ro/pocket-dictionary/download.html
Source : 1800pocketpc.com
2. WordNet is an online lexical reference system whose design is inspired by current psycholinguistic theories of human lexical memory. English nouns, verbs, adjectives and adverbs are organized into synonym sets, each representing one underlying lexical concept. Different relations link the synonym sets each representing one underlying lexical concept. Different relations link the synonym sets.
Installation
Firstly, you need WordNet 2.1. The WordNet 2.1 dictionary in a default install on a PC is in c:\Program Files\WordNet\2.1\dict. The dictionary needs to be copied to the storage card in the form of (eg) \Storage Card\WN21\dict\.
Download WordNet Dictionary : WordNet 2.1
Source: 1800pocketpc.com
3. Download Pocket Dictionary : CAB download (4.38 MB)
Download : http://freewareppc.com/educational/pocketdictionary.shtml