Hacker

 HACKER [originally, someone who makes furniture with an axe] n. 1. A
       person who enjoys learning the details of programming systems and how
       to stretch their capabilities, as opposed to most users who prefer to
       learn only the minimum necessary. 2. One who programs
       enthusiastically, or who enjoys programming rather than just
       theorizing about programming. 3. A person capable of appreciating hack
       value (q.v.). 4. A person who is good at programming quickly. Not
       everything a hacker produces is a hack. 5. An expert at a particular
       program, or one who frequently does work using it or on it; example:
       "A SAIL hacker". (Definitions 1 to 5 are correlated, and
       people who fit them congregate.) 6. A malicious or inquisitive meddler
       who tries to discover information by poking around. Hence
       "password hacker", "network hacker".