Rsh

remote shell, one of the many r* services that allowed remote actions across different unix computers. Like it's other r-services siblings (rlogin, etc) it was unencrypted and is now deprecated for remote access tools that offer better security, like ssh, scp, etc.

It should be noted that "deprecated" means heavily deprecated, in this instance - the r?? services are not running by default on any modern FreeBSD machine and it is HIGHLY recommended that you not enable or attempt to use them.