Allows you to specify nicks that will not be able to send private messages or notices on that specific server. You can also shun a user from speaking in a particular room; this will not affect private messages at all. To remove the shun, just issue the UNSHUN command with the specific nick you wish to unshun. To view the shun list type /shun. Opers cannot be shunned. However if a shunned user opers, the shun still remains and is effective until it is removed. If you send the SHUN command without any parameters you will see the entire shun list.
Examples:
/shun Mark testing
/shun #WebMaster Mark
This can be used on people who have been harassing or flooding people through private messages or notices. They can still talk in rooms, but the room operators can keep an eye on things. They can also use other servers where they are not shunned, if there are any. This can be a rather harsh thing to do to someone because unless you inform them, they will have no way of knowing that they are shunned and their private messages are not being received. It can be used in rooms if a particular user is causing problems there, but generally behaving elsewhere.