2) One who is academically superior to the normal population.
We don't like to rub it in... oh wait, yeah we do! PNEUMONOULTRAMICROSCOPICSILICOVOLCANOCONIOSIS!!
Once-Popular Kid: Please, my tumor's growing!!!
Me: Hrmmmmm... Well, you should have considered this possibility when you decided that only nerds go to college.
Often mistaken for Geeks, who aspire to become nerds, yet lack the intelligence, and end up giving nerds a bad name due to their poor social skills.
Non-nerds are often scared of nerds, due to their detailed knowledge, and therefore seemingly high levels of intelligence - and subsequently denegrate them as much as possible as often as possible.
Nerds exist covertly within the fabric of society, often choosing to 'nerd it up' in private or in the company of fellow nerds. It is for this reason they are feared the most - unlike geeks, who are easily identified, nerds can only be found out when casual conversation reaches a subject that they like nerding.
Nerd: "Let's bash this nerd"
Nerd: "That'll teach you to go playing with my tesla coil"