Ephemeral Feature Toggles
At its simplest feature toggle is a small if-statement, which may be toggled without deploying code, and used to enable features (new or changed functionality) in your software.
In an agile setup most developers love having feature toggles available, as they often allow for a continuous delivery setup with very little friction and obstacles. While this is true, it often seems developers forget to think of feature toggles as ephemeral, and doesn’t realize what a terrible mess, this can cause - given they don’t remove the toggles once the feature is launched and part of the product.