Sentence:  In 1884 Greathead was part of a syndicate that obtained powers for another <WSD>subway</WSD> - 'The City of London & Southwark Subway'. The term <WSD>'subway</WSD>' sounded more sophisticated than 'underground railway', which was associated with the sulphurous Metropolitan, and it would be adopted by New York for its own electric metro when work started on that in 1904. 
Meaning of the word marked with <WSD> tags:  An underground railway, especially for mass transit of people in urban areas. (Rail transportation)