进程开发领域，代码中的任何可能导致深层次问题的症状都可以叫做代码异味.

通常，在对代码做简短的反馈迭代时，代码异味会暴露出一些深层次的问题，这里的反馈迭代，是指以一种小范围的、可控的方式重构代码。基于这些暴露的问题，人们会进一步的检查设计和代码中是否还存在别的代码异味，然后再做进一步的重构。从负责重构的开发者的角度来看，代码异味可以启发何时重构，如何重构。因此，可以说代码异味推动着重构的进行。

该术语似乎由Kent Beck于90年代后期，在WardsWiki上首次使用。且自从在Refactoring. Improving the Design of Existing Code.被提到过，使用率就大大的提高。代码异味同时也是敏捷开发者常用的术语。

Code smell, also known as bad smell, in computer programming code, refers to any symptom in the source code of a program that possibly indicates a deeper problem. According to Martin Fowler, "a code smell is a surface indication that usually corresponds to a deeper problem in the system". Another way to look at smells is with respect to principles and quality: "smells are certain structures in the code that indicate violation of fundamental design principles and negatively impact design quality". Code smells are usually not bugs—they are not technically incorrect and do not currently prevent the program from functioning. Instead, they indicate weaknesses in design that may be slowing down development or increasing the risk of bugs or failures in the future. Bad code smells can be an indicator of factors that contribute to technical debt. Robert C. Martin calls a list of code smells a "value system" for software craftsmanship.