There were 4 definitions of geek from dictionary.com. Here’s one of them :

geek /gik/ Pronunciation Key – Show Spelled Pronunciation[geek] Pronunciation Key – Show IPA Pronunciation

–noun Slang.

1.	a carnival performer who performs sensationally morbid or disgusting acts, as biting off the head of a live chicken.

2.	a peculiar or offensive person, esp. one who is perceived to be overly intellectual.

3.	an expert in computers (a term of pride as self-reference, but often considered offensive when used by outsiders.)

---

[Origin: 1915–20; prob. var. of geck (mainly Scots) fool < D or LG gek]

Dictionary.com Unabridged (v 1.0.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.

In the Our Living Languange section it also stated that :

Our word geek is now chiefly associated with contemporary student and computer slang, as in computer geek. In fact, geek is first attested in 1876 with the meaning “fool,” and it later also came to mean “a performer engaging in bizarre acts like biting the head off a live chicken.” Perhaps the use of geek to describe a circus sideshow has contributed to its current popularity. The circus was a much more significant source of entertainment in the United States in the 19th and early 20th centuries than it is now, and large numbers of traveling circuses left a cultural legacy in various unexpected ways. Superman and other comic book superheroes owe much of their look to circus acrobats, who were similarly costumed in capes and tights. We also owe the word ballyhoo to the circus; its ultimate origin is unknown, but in the late 1800s it referred to a flamboyant free musical performance conducted outside a circus with the goal of luring customers to buy tickets to the shows inside. Other words and expressions with circus origins include bandwagon (coined by P.T. Barnum in 1855) and Siamese twin.

Then the definiton of computer geek was :

computer geek jargon
(Or “turbo nerd”, “turbo geek”) One who eats (computer) bugs for a living. One who fulfils all the dreariest negative stereotypes about hackers: an asocial, malodourous, pasty-faced monomaniac with all the personality of a cheese grater. The term cannot be used by outsiders without implied insult to all hackers; compare black-on-black usage of “nigger”. A computer geek may be either a fundamentally clueless individual or a proto-hacker in larval stage.
See also Alpha Geek, propeller head, clustergeeking, geek out, wannabee, terminal junkie, spod, weenie.
[The Jargon File]
(1997-06-26)

The Free On-line Dictionary of Computing, © 1993-2006 Denis Howe

So who’s a geek? Let’s hear it!