Specialized functional division in an organization or department. It is used in a broader sense and even includes different groupings in the organization, from business area down to smaller groups/teams.

Core vs Extended

Description 

Usually, every organizational unit has its own chief officer and reporting structure.

Reference to Standards

SKL/Inera: Has Organizational Unit with the same meaning. Definition: Not confirmed yet.

Archimate: Does not have Organizational Unit specifically, but uses instad Actor (Business Actor) in a broader sense. 

TOGAF: Has Organizational Unit with the same meaning.