USERHOST

Usage: USERHOST <nickname> <nickname>

Returns the user@host information for up to five users at a time.

Example:
/userhost josh phil

If you just want the address for some users this is a faster way to retrieve them than individually whoising each of them. It also only returns the mask, unlike the whois command that will several lines of information. You might want to userhost some people if you needed their mask to identify them.