Yes, CHATROOM is a Scrabble word!

Letter values in Scrabble US: C 3, H 4, A 1, T 1, R 1, O 1, O 1, M 3.

Is it a valid word?

CHATROOM is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a site on the internet where a number of users can communicate in real time (typically one dedicated to a particular topic)

Also: chat room.