Code Rot

Definitions

The gradual decline of a codebase’s usefulness or maintainability as dependencies change, assumptions drift, documentation ages, and no one actively tends the system. It does not mean code literally changes by itself; it describes software becoming effectively stale in its environment.
In plain English: Software becoming outdated and harder to use or maintain over time.
Example: "That integration suffered code rot after the upstream API changed three times and nobody updated the adapter."