n. A knowledgeable and experienced Internet user.
"The best method for learning your way around the Internet is to read as much as you can (especially the Frequently Asked Questions lists associated with some Web sites, mailing lists, and newsgroups), learn the ins and outs of Netiquette, and to ask questions. Thus does the 'newbie' turn into a 'knowbie'."
This word is a play on newbie, a common term for an neophyte Internet user. (Once used only in the Usenet realm, but now applicable to the Internet as a whole.)