A technically oriented person. It has typically implied a "nerdy" or "weird" personality, someone with limited social skills who likes to tinker with scientific or high-tech projects. The origin of the term dates back to the late 1800s. A geek was a carnival performer who bit off the head of a chicken or was part of a freak show.
Much More in Vogue Today
By the end of the 1990s, it became quite fashionable to be a geek, since countless technical people had become very successful, starting with PCs in the 1980s and throughout the dot-com bubble. See uber geek
From "The Best of The Joy of Tech" cartoon book by Nitrozac and Snaggy (O'Reilly & Associates, Inc., 2003, ISBN 0-596-00578-4). (Image courtesy of GeekCulture, www.geekculture.com)