Kahlimat is a vocabulary trainer app that allows you to share words with your friends and language tandem partners. You can send/request not only the definition of the word, but also record the pronunciation right in the app.
Learn your personal vocabulary list with the practice function that offers different types of learning cards (e.g. a simple flash card, multiple choice, typing test) and uses a spaced-repetition algorithm to optimize your learning frequency.
To use the app you need to sign in with a Google account. All your words, learning progress, friendlist and messages will be saved in the cloud and are accessible via any device you use the app with.
The app supports any language, but its user interface is English only.