Big Ball of Mud

This quote from yosefk.com sums up the article more or less:

One of the key traits of good code is the ease at which it can be modified. One of the key traits of bad code is the high cost of modifying it. So good code is likely to deteriorate until it’s bad enough to become hard to change, and bad code is likely to stay bad. In short, code has a strong tendency to end up bad.