I think the Jargon File (http://www.catb.org/jargon/html/index.html http://www.catb.org/jargon/html/index.html) puts it nicely.. there are several definitions,

I think the Jargon File (http://www.catb.org/jargon/html/index.html http://www.catb.org/jargon/html/index.html) puts it nicely.. there are several definitions, most having to do with technical adeptness and a delight in solving problems and overcoming limits.