A Culture Code is a description of the culture of an organisation. It covers not just what you do, but also why you do what you do. It is like the employee handbook for purpose-driven companies in the 21st century. One way or another, a Culture Code usually covers an organization's purpose, values, behaviours, rituals and recognition programs.
(This practice is under development and is part of the book Startup, Scaleup, Screwup.)