Master Black Belt (MBB)

A role in Six Sigma by someone who has a very strong expertise in the Six Sigma (and possibly Lean) tools and concepts. The actual functions and responsibilities for this role vary but in general this person has a full-time dedication to leading multiple projects that yield considerably large benefits for the organization. Their projects generally cover a longer timeframe (like 3 to 6 months) and their role usually involves managing a Six Sigma program and/or mentoring Black Belts or Green Belts. This is a role that is not commonly certified by training organizations, but is often treated as a title by responsibility without necessarily having a certification.
Related StatStuff Video: 
   -Section 1-Introduction, Lesson #8 - Key Roles in a Lean or Six Sigma Project