Adding Functionality to Your Cube - Getting Started with SQL Server 2012 Cube Development - page 164

Note
Sometimes, when you create user-defined hierarchies, you do not have
the same number of levels in each node. This is called a ragged hier-
archy . More information about ragged hierarchies can be found at ht-
tp://msdn.microsoft.com/en-us/library/ms365406.aspx .