It seems that everyone has very different definitions for geek, nerd, and dork. I would like to help create a more concrete definition for each of these. Below are my own definitions and I invite you to add your own in the comments.

Geek: A person who is completely obsessed with any particular subject. Often, the subject is technological in nature but that is by no means required. As a result of this obsession, the geek is rarely accepted by popular culture.

Nerd: A person devoid of all social skills. A true nerd has much difficulty communicating with others and often shows this through his/her clothing and hygene.

Dork: Similar to a nerd, but much cuter. It has more to do with an attitude. In other words, when people deal with a certain stimulus in an unexpected, and often slightly nerdy, way. Dork is the most subjective of the three.