To Wish I Had a One Track Mind

What makes one a genius? Einstein couldn't tie his shoes, flunked out of math class, and yet is hailed as the greatest mind of the 20th century (and certainly on the top ten list of history). This man, Steven Wiltshire, is called autistic. Does one have to be a renaissance man to be a genius?
The jack of all trades or the great master of one?

Let's take it a step further. Does genius comprise merely of natural talent as apposed to cultivated skill? Is it limited to the intellect or can it also describe physical achievement, willpower, or tenacity?

In short, what is genius and does it lie hidden within each of us simply waiting to be voiced? One could spend 20 lifetimes searching for that perfect phrase to speak - perhaps it's a blessing to have fewer words to choose from.