A clueless coworker is a documentation debugging tool consisting of a coworker who does not know the details of the work you are involved with, preferably with as little background knowledge as the average person who would be using the documentation, or possibly as the average entry-level person who would be using the documentation.

EdGrimm discusses the testing value of such coworkers as part of the TooMuchDocumentation discussion.

''The description suggests the term is non-derogatory. Perhaps the titles uses some older meaning of clueless which the average techie has forgotten?''

Quite right... clueless in that they don't have any clues with which to approach using the system