kill <nick> <comment>

The kill server command is used by irc operators to forcibly eject a client from the irc newtork. Local operators usually can kill users on their own server, and global opers usually can kill any user on the network.

As a side effect of this ejection, the person will be removed from all of the channels they are on, so they would lose any channel operatorships.

IRC servers generally require you to provide the comment.

Most irc clients (including this one) will automatically reconnect a client that is killed from a network, so killing someone is not an effective way to get rid of them, although it does bring you to their attention.