Meaning

• A carnival performer specializing in bizarre and unappetizing behavior.

  "I once saw a geek bite the head off a live chicken."

• A person who is intensely interested in a particular field or hobby and often having limited or nonstandard social skills. Often used with an attributive noun.

  "I was a complete computer geek in high school, but I get out a lot more now."

• (by extension) An expert in a technical field, particularly one having to do with computers.

  "Do you need a hardware geek or a software geek?"

• The subculture of geeks; an esoteric subject of interest that is marginal to the social mainstream; the philosophy, events, and physical artifacts of geeks; geekness.

• An unfashionable or socially undesirable person.

  "Why do you hang around with them? They’re just geeks."

Meaning

• To behave geekishly or in a socially awkward manner, especially when under the influence of drugs or other psycho-active substances, and exhibiting such marked characteristics as hyperactivity, repetitiveness, talkativeness, nervousness, irritability, or paranoia.

  "Hey, check out that guy...he's really geeking out pretty bad."