Since Wiki provides the ability to edit any WikiPage, and is therefore constantly evolving, some consider every WikiPage to be a WorkInProgress. WorkInProgress is often used more specifically as a WikiTag on a WikiPage that is currently under development.
The most obvious sign of a WorkInProgress wiki page is that much of the content is in ThreadMode conversation. As development nears "completion", ThreadMode comments are sometimes moved into a new WikiPage of the same title with the suffix Discussion. The valuable content from the discussion is then refactored back into the original page. In many cases, this refactoring is comprehensive enough that the discussion page becomes unnecessary.
In general, a product or project past the inception stage but prior to the completion stage is also considered to be a WorkInProgress.
My Convention - some guidelines
See also: AnalogyBetweenProgrammingAndManufacturing, ManufacturingRoadmap NotInGeekSpeak