IPA: /ˈtʃætˌruːm/
KK: /ˈtʃætˌrum/
A place on the internet where people can talk to each other in real time using text.
I met some new friends in the chatroom last night.
Chatroom → It is formed from "chat" (from Middle English *chatten*, meaning to talk or chatter) and "room" (from Old English *rum*, meaning space or area). A chatroom is a space designated for talking or chatting online.
Think of a place where people come together to 'talk' ('chat') in a designated 'space' ('room') — that's what a chatroom is.