› a piece of cloth or other material that hangs across a window or space to decorate a room or to make it dark or private: In the restaurant, arches covered with beaded curtains divide the room. › In a theater, the curtain is a large, movable sheet of heavy material that separates the stage from the area where people are sitting. › The curtain is also the time at which a performance begins: The curtain is at 8 o’clock.