Dictionary - Merriam-Webster
In addition to all the definitions from Merriam-Webster's Collegiate Dictionary, this app offers voice search – to let you look up a word without having to spell it – along with synonyms, antonyms, example sentences, Word of the Day, and more. It’s a great tool for reference, education, and vocabulary building.
The app is free
More information: http://www.merriam-webster.com/apps