The term "cold-water flat" is an architectural term that refers to a style of apartment that is characteristically narrow, with multiple rooms arranged in a linear fashion and accessible through a single hallway. However, this term is less commonly used nowadays, and there are several synonyms that are more commonly used to describe these apartments. Some synonyms for "cold-water flat" include railroad apartment, shotgun-style apartment, tenement apartment, and basement apartment. Each of these terms describes the same type of narrow, often outdated and poorly designed living space that was popular in the early 20th century. Despite their outdated designs, these apartments often hold historical value and can have charm and character.