/notice is a
command found in
IRC. In many ways it can be looked upon as comparable to
/msg, though its exact workings are somewhat different. While
/msg will open a dedicated chat
window on the recipient's end, inviting a direct reply, a /notice will in most
clients simply result in a highlighted message appearing in the main
channel window of the recipient, and in some will also cause a beep to sound.
As such, /notice is quite handy for sending short messages where a reply is not expected. Its most common use is in fserve and XDCC advertisements replying to a !list or xdcc list command, so that the person requesting the list is not bombarded with new windows. Of course, it can also just be used in chat if you want to send someone a short message, but don't want to use /msg.