CHANNEL MODE p

Usage: MODE <channel> +|-p
p - Private
Hides the channel in the channel LIST and WHOIS information, this is a good setting for channels that do not wish to have random people wandering in. It does not prevent anyone from joining, but it keeps the channel from being easily noticed.
Privilege: channel operator
Examples:
/mode #movies +p
Note: This mode is equivalent to CMODE +s.