The term 'plaster of Paris' is a building material used for coating walls and ceilings. It is made from gypsum, which is heated to form a dry powder that can be mixed with water to form a paste. The answer to the crossword puzzle is PARIS, which is the capital of France and the most populous city in the country. Plaster of Paris was first used in Paris in the 19th century and has since become a popular building material around the world.