Right-click the required table definition and select 
                     			 Delete Table Definition. 
                     			 
                     Tip: You can select multiple table definitions to delete by holding the 
                        				SHIFT key when clicking. Only items under the same file definition can be selected at once.
                        			 
                     
                     			 
                     Note: The Catalog Explorer also contains a 
                        				Table Definitions node, where all tables (regardless of which file definition they are derived) are listed; you can also right-click this node
                        and select 
                        				Copy Table Definition. 
                        			 
                     
 
                     			 
                     A confirmation box is displayed if the table definition contains table instances.