The term 'Siding Railroad' is a type of railway track that branches off from the main line and is used to store rolling stock or allow trains to pass each other. The crossword solution for this term is 'SPUR', which is a four-letter word meaning a short track branching off from a main line. Siding Railroads are typically used to store rolling stock, such as freight cars, or to allow two trains to pass each other without having to switch tracks.