Someone who is passionate about their technology or field, and is normally quite good a it.
For example, a Hacker might be a Geek. But you can equally have law geeks or astronomy geeks or even rugby geeks!
Nerd tends to be a word reserved for someone who is tied up in their passion so much they don't see anything else; like time for PersonalHygiene or stepping into the BigBlueRoom.
See GeeksAndGirls and Geekerata
