To delete a security group rule, use the openstack security group rule delete command and specify the ID or name of the security group rule:
openstack security group rule delete <group> [<group> ...]
To delete a security group named MySampleSecGrpRule80, you can enter the following command:
openstack security group rule delete MySampleSecGrpRule80
Multiple security groups can also be deleted simultaneously, like so:
openstack security group delete MySampleSecGrpRuleTcp80 MySampleSecGrpRuleUDP123
While it is possible to delete the rules within the default security group, it is not possible to delete the group itself.