groupdel - delete a group
groupdel command modifies the system account files, deleting all entries that refer to group. The named group must exist.
You must manually check all file systems to insure that no files remain with the named group as the file group ID.
In this example, the groupdel command would delete the group newgroup.
$ groupdel newgroup
# grep newgroup /etc/group
no output on screen as there will be no entry in /etc/group