To make a concept (such as code) inherently not understandable, either for artistic or security purposes. To make code which is not understandable but still executes, usually to fill a specification. For example, the following C++ of mine:

void BottlesOfBeer(int age) {const ostream*__=&cout;int _; for(_^=_^(age>=21?100:_^_);(_^_<_?*__<<_<<" bottles of beer on the wall\n",(int)__:_);_+=_+~_);

The act is obfuscation.