Merriam-Webster, one of the best-known publishing houses for reference books in the world, has a mobile version of its popular dictionary, the Merriam-Webster Dictionary.
Used by millions all over the world, this tool offers a different way of understanding the English language. In this mobile version, you can listen to the pronunciation of any word whenever you want.
It's very useful for both those who are just starting to learn English as well as the most experienced native speakers. It also includes a history of the construction of English vocabulary, word by word.
In this fantastic dictionary you'll find comprehensive definitions of every word, with all the definitions, example sentences, etymologies, and synonyms for each.
You can also search by voice, which will help you practice, and you can even mark words as favorites so you can access them more easily.