App Creep refers to the uncontrolled additions or continuous growth of apps on an individuals smartphone(device). This phenomenon occurs when the App Store is utilized in a reckless manner and the acquirement of apps is not properly defined, documented, managed or controlled. It is generally considered a negative occurrence, and therefore should be avoided.
Amazed friend: "Dude you got like 5000 productivity apps on your smart phone!"
You: "Yeah, I have a serious case of app creep."