This adds a temporary qline to the server. Qlines restrict the use of a nickname to network operators. If you notice that a certain nickname is connected to your server and that nickname is inappropriate, you can use this command to change the nickname of that user to Guestxxxx and prevent further use. Note: that nickname will not be available for use until it is removed from the qline list. To view your qline list simply type /stats q on your server, the qlines are prefixed by q:.
/qline badname offensive nickname
Qlines are used to prevent nicks that seem in bad taste or nicks that give the illusion of being part of the network administration. This is why opers can use qlined nicks. Be careful when setting qlines with variables, such as *sh*t* which would ban possibly acceptable nicks like Lipshitz.