A full version program for Android, by Merriam-Webster Inc..

Learner’s Dictionary – English helps improve your written and verbal English-language skills, regardless if you’re a beginner or a fluent English speaker. This dictionary contains thousands of easy-to-understand definitions and sentence examples of words and idiomatic expressions. 

You can add the words you’ve learned using the app’s Favorites, which serves as a list of the new words you’ve learned the definitions of so far. Learning the pronunciation of a word is easy as you only need to tap on the speaker button. All words are pronounced in American English by native speakers. Also, you can check out Merriam-Webster’s Word of the Day to learn new (and perhaps, unusual) idioms and verbal phrases.