It's relatively a new term used recent times as many company
now a days are looking for security of the networks too.
Each and every company will have there own internal
terminology. we can call it as Security assessment also.

 At its simplest, a penetration-test is the process of
actively evaluating your information security measures.The
information systems will be tested to find any security
issues, as opposed to a solely theoretical or paper-based audit.

The results of the assessment will then be documented in a
report, which should be presented at a debriefing session,
where questions can be answered and corrective strategies
can be freely discussed.

penetration matrix is a collection of rows & collums, which 
identify 
1)potential perpetrators.
2)potential point of penetration.