[countable] a part of a building that has its own walls, floor and ceiling and is usually used for a particular purpose He walked out of the room and slammed the door. They were in the next room and we could hear every word they said. a dining/living/sitting room They had to sit in the waiting room for an hour. I think Simon is in his room (= bedroom). I don't want to watch television. I'll be in the other room (= a different room).