The term WikiGnome is one created by wiki enthusiasts to describe a certain type of participant. A Wiki Gnome is one who is generally inobtrusive and will do behind-the-scenes research on topics which are hinted upon but not expounded upon. These are the people who will quietly fix your links and spelling, link pages together and do general tidying.
When a page becomes obviously dated, some wiki gnomes become bold and will step in and "do it right" by refactoring a page, or cutting and piecing a topic apart to put it's content into other pages.
There are different kinds of wiki gnomes, just as they are many kinds of people. Some are vigerous on reinforcing what they see as "standards" and will correct links, spelling and punctuation without thought to an author. Some will wait for pages to become stale before moving in. Where some wiki gnomes correct spelling, others enjoy going off on walkabouts researching links for a topic they found interesting a moment ago. Some will thereby create lists of interesting links appropriate to a topic, but still others will organizing existing material to make it more presentable. Most wiki gnomes try to be inobtrusive and helpful, acting as a serf to noble topic-contributors.
Generally speaking, the presence of an active wiki gnome indicates great interest and potential for a wiki. The more authorship or original content there exists in a host wiki, the greater the wiki gnome activity.
(original text borrowed from http://www.infoanarchy.org/wiki/wiki.pl?Wiki_Gnome)