From TechWriter Wiki
A guerrilla wiki is a wiki requiring no or minimal installation that can be used, generally in a corporate environment, as an alternative to hosting a wiki server.
Because of the red tape involved in allocating IT resources to hosting a wiki server and the restrictions placed on regular user computers, it is often difficult or impossible to install a wiki in a corporate environment. Similarly, it is generally a violation of security policy to post sensitive corporate information on an externally managed wiki. Therefore, employees in need of a wiki can place a guerrilla wiki, generally in the form of a small program or HTML file that requires no installation, onto a shared drive to be used in lieu of an "official" wiki.
An example of a guerrilla wiki is TiddlyWiki.