The Forum / The FORVM
Alternative spelling added as suggested by Ben Kovitz.
It's both Latin and English. It's a short, single word that is easily referred to: "please take it to the forum" is a lot nicer to say than "please discuss that in chat" or "please move the discussion to [Insert Latin Phrase Here]"
It's also intuitive and perfectly encompasses what chatrooms are on StackExchange: an extension of the site for users to come together for the purpose of discussion.
As a bonus I like the historical tie to Ancient Rome which had the most famous forum of all.
forum (plural forums or fora)
A place for discussion.
A gathering for the purpose of discussion.
A form of discussion involving a panel of presenters and often participation by members of the audience.
(Internet) An Internet message board where users can post messages regarding one or more topics of discussion.