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 when geeks were carnival performers who did freaky things like biting off the head of a chicken. See uber geek
Very Much in Vogue Today
After technical people became millionaires and billionaires, it became fashionable to say you were a geek. The Geek Squad is Best Buy's technical support and repair department.
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)