Ovinomancer
No flips for you!
To elaborate a little, it is a characteristic of geniuses that they profoundly change the way we think about the world. This is hard to do and most people never achieve it. Only a very few people succeed.
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In D&D terms, the Hermit background might be good. The PC has made a great discovery, loses no opportunity to try to convince everyone that he is right and gets annoyed when people fail to understand him. Those who do understand him all agree that his discovery is a work of genius. None of this requires him to have any particular Int score. If he has a low Int and fails to solve mundane problems that require ability checks, it's because he is too pre-occupied with his own thoughts to bend his mind to the here and now. See? It works.
That's an... odd definition. It's outcome based: you have to change the thinking of people about the world in a profound way. Unless you do this, you're not a genius? Then, it remains to be seen that the hermit is a genius -- unless he changes profoundly the thinking of people about the world, then he's not, regardless of the depth of insight of his discovery.
EDIT: Also, this means that many religious leaders are geniuses, because they profoundly change thinking about the world for many, many people. Not sure that's a functional definition if a conversion counts as genius. Or, would you mean that the person must come up with the profound thoughts themselves? If so, L Ron Hubbard wants a citation for genius.
EDIT2: Oh, and my kids want genius certification. They definitely affected my thinking about the world in a most profound manner.
You're welcome to your individual definition of the word, but I'm not certain that's a very useful definition.
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