The word geek is a slang term for odd or non-mainstream people, with different connotations ranging from "a computer expert or enthusiast" to "a person heavily interested in a hobby", with a general pejorative meaning of "a peculiar or otherwise dislikable person, esp one who is perceived to be overly intellectual".
Although often considered as a pejorative, the term is also often used self-referentially without malice or as a source of pride.
Read more about Geek: Etymology, Definitions, Geek Chic