A smart dude who spends more time on important things like their intelligence than thing like sports, and as a result are socially inept. I myself am a lesser nerd, because I devote my time to other, non-nerdy things such as popularity, running (the nerd sport, but oddly enough better for you than weight training and sports like football) and making people laugh. I belong to a sub-group of funny nerds who don't have snot-coated sleeves,and do have girlfriends. Most people don't know I'm a nerd.
ME: I'm a nerd.
Brainless Jock Who Thinks I'm Cool:...No your not!
ME: Yes, I am.
Today the middle finger means "FUCK YOU!", but was actually invented in Golden-Age Athens 2500 years ago, not Medieval times. It originated from Ancient Greek comedy called The Clouds by Aristophanes. In this play, the actors mocked a politician by stating that his competitor had a longer dick. They showed this by running around with their middle finger pointing out from their dick area. It was meant to be stupid. It's meaning changed over time, but always was considered insulting.
Girls actually insult themselves when they give people the middle finger, but is also very offensive to men.