Wordchain (GitHub: sonnylazuardi / wordchain, License: MIT) by Sonny Lazuardi is a multiplayer word game made with Firebase, AngularJS, the Google Dictionary API, and the Wikitionary API. It allows you to sign in with Facebook, and complete words in a crossword-like manner.
The code is all modular, dependency-injected Angular classes, so it's fairly easy to see how it fits together. The main game logic is in js/controllers.js. Here's the dictionary API search: