A person who does not like CowboyCoding but is so damn good that when they shoot from the hip they hit the target every time. The thing that an anonymous genius finds hardest about writing code that is as bug free as the customer is willing to pay for, is:
getting the definition.
writing it so that other people will be able to understand it.
remembering which are the bits of the language that most people don't understand.
An anonymous genius is a person who you recognise as a genius before they tell you that they are a genius.
An AnonymousGenius typically does not think that being one is important enough to warrant mentioning.
An anonymous genius when writing code is likely to be a RealProgrammer, and not a wanna be programmer.
For an AnonymousGenius being a RealProgrammer is just a day job. At night they might be a RealParent? or a RealFriend?.