Usage patterns
〈場所〉の待合室で待つto wait in the waiting room of a place
I waited for thirty minutes in the hospital's waiting room.
待合室で名前を呼ばれるto have one's name called in the waiting room
When your name is called in the waiting room, please go into the examination room.
待合室に座るto sit in the waiting room
He was sitting in the waiting room reading a newspaper.