Let me add my two cents worth.
Psuedocode is as Oppenheimer described it.
DBMS - Database Management System - As the name suggests it is not the actual database but the management system that interfaces with programs, developers and end users to allow for ddl, dml and standard queries to be peformed on the database.
RDBMS - Relational Database Management System - An RDBMS is a DBMS that runs on a relational database.
Example. ACCESS Database.
ODBMS - Object Database Management System - AN ODBMS is a DBMS that runs on an Object Database.
Example. Jasmine.
ORDBMS - Object Relational Database Management System - An ORDBMS is a hybrid DBMS that runs on an object relational database.
Example. Oracle 8.