Dan would like an app that will translate acronyms and abbreviations into real words. Leo says there isn't one he knows of, but it's a great idea. The Kindle has something similar though. By pressing and holding, it will open up a dictionary to define it. The Mac also has that feature CMD-Shift-D. But phones are harder because they isolate, or sandbox, each app for security reasons -especially iOS devices. You could look for a browser extension that could do it.
From the chatroom - click and hold down a word in iOS and tap "look up." It will popup the definition. You can also double click it. Android does something similar in Chrome - Long press a word in Chrome on Android and it will pop up a Google definition and search.