A polite, euphemistic term for a restroom, often used in public places like department stores or hotels. More refined than トイレ.
The powder room is at the end of that hallway.
デパートの化粧室はいつも清潔で、鏡が大きい。
The restrooms in department stores are always clean and have large mirrors.
化粧室 is a formal euphemism seen in department stores and hotels, whereas お手洗い is the everyday polite word used in ordinary conversation.
化粧室 is a polite, formal term used in public announcements, similar in register to ラバトリー but more common in everyday signage.
化粧室 is a more formal or upscale term (often used in hotels or department stores) for the same kind of washroom as 洗面所.
Compound of 化粧 (makeup) and 室 (room), literally 'makeup room', reflecting its origin as a place for women to touch up their appearance.