This document explains why a KB document may appear in the KB Admin Tools with the status label set to "Undefined".
Typically, when you view a document in the KB Admin Tools, you will see a document status listed after the document ID in the heading, e.g. Active, In Progress, In Review, etc. Which status you see depends partially on how you got to the document.
In some cases, you may instead see the label "Undefined" appear in parantheses after the doc ID in lieu of one of the normal statuses.
This label appears if you were previously browsing documents in the KB Admin Tools, and you selected "All status" from the Status dropdown filter. When viewing documents with this option selected, the links do not specify any one status, so the label will instead read "Undefined".
You can scroll down to the bottom of the page to see the actual document status(es) listed in the SiteStatus section of the document info table.