A coal bunker is a storage space for coal, but there are several alternative words used to describe similar structures. One option is a coal bin, which is typically smaller than a bunker and may refer to a storage area inside a building. A coal silo is a tall, cylindrical structure used in industrial settings to hold large quantities of coal. Another option is a coal shed, which may be an outdoor storage space or a small room connected to a building. Other synonyms for a coal bunker might include a coal store, a coal vault, or a coal house, depending on the size and location of the storage space.