rat's nest

1. (idiomatic)Something that is excessively complicated, entangled, or disorderly (either physically or metaphorically).

   rat's nest of a wiring harness

2. Something that is excessively complicated, entangled, or disorderly (either physically or metaphorically).

   (idiomatic)A software or hardware system whose design lacks organized structure, making it difficult to understand and maintain.

   2016 July 2, veryatlantic, "Saturday, July 2, 2016: Addendum," Tales From The Trailer Court™ (retrieved 2 March 2017):

   Think of libraries as the way the sub-idiots who like C code hide all the rat's-nest programming they don't want you to see.

regular