Dictionary.com is one of the best online reference websites, and is useful to find meanings of any terms you need. And it has now released a free iPhone and iPod touch App which can help you find more than 275,000 definitions and around 80,000 synonyms from your iPhone anytime.

The free Dictionary.com app delivers world-class reference content from Dictionary.com and Thesaurus.com including more than 275,000 definitions and 80,000 synonyms. The app also features audio pronunciations, similarly spelled words and Dictionary.com’s popular Word of the Day that is enjoyed by more than a million users.

The features of the app include -

• Alphabetical indexing
• Similarly spelled words
• Spelling and audio pronunciation
• Example sentences
• Non-standard uses
• Word origin and history

Its not only Dictionary.com that would be working here, but Thesaurus also would be helping with loading of data like synonyms etc.
This app works in both iPhone and iPod touch which is updated with the latest 2.0+ software.
The word page shows main entry, synonyms, definition and the origin of the word if the info is available on the original website.

You can download the Dictionary app from here. It is advised to download the app by opening the iTunes store through the iTunes app in your computer.