DROP TYPE typename [, ...]
The sole parameter of this command is the name of an existing type you wish to remove.
Use the DROP TYPE command to remove a type from the database system. Only the owner of a type will be allowed to remove it.
If you are logged in as a superuser account, you will be able to drop system types. This can cause extreme instability. Be careful!
This command will not automatically remove any objects that reference the data type. Once the data type is removed, anything that uses it will most likely stop working. Be sure to remove these objects.