The Free On-line Dictionary of Computing (30 December 2018):

hierarchical database

    A kind of database management system that links
   records together like a family tree such that each record type
   has only one owner, e.g. an order is owned by only one
   customer.  Hierarchical structures were widely used in the
   first mainframe database management systems.  However, due
   to their restrictions, they often cannot be used to relate
   structures that exist in the real world.