Definition - What does Hairball mean?
In IT, pros use the term “hairball” to refer to any jumbled, confusing, inefficient or unnecessarily large piece of code, or for some other tangled mess. When applied to code, “hairball” implies a number of things, including a lack of utility and a lack of user friendly design.
Techopedia explains Hairball
When people talk about a hairball, they may be talking about code that is poorly written. It may have too many comments or poorly placed comments, along with unnecessary intrusions to efficient design. In some cases, the code uses too many operators and commands to do a job. There may be a “circular” design of references where code points to other code in a less than efficient way. Any of these, along with other undesirable code elements, may result in developers or others calling a piece of code a hairball. Another insinuation with this term is that the design of the code makes the product difficult to use.