Every yin has its yang, and every hero has their dark side, and so the very existence of patterns suggest that there exists the opposite. We could simply call it a mess, but programmers try to find an order to everything, even in chaos, and so they cataloged the mess and described the many kinds of anti-patterns. I will only briefly touch on this topic, as the goal of this book is to teach you about order, not disorder, but there is always something to learn from bad examples.
Design patterns are nicely classified, and most programmers agree on how they should be named and defined. Anti-patterns, on the other hand, are messier. They hide behind different names and they provide mere sketches of behavior, not fully defined templates.
The nastiest of the anti-patterns is sometimes called a big ball of mud. A typical sign of this anti-pattern is that the code is a mess...