STB is a short way of writing the Surface Transportation Board. It is a government body in the United States. Its job is to watch over things that move goods and people across the country on land — mainly the freight railways, and also some bus companies and pipelines. When a big railway company wants to buy another railway company, or wants to close a line, or when a customer says a railway is charging unfair prices, the STB is the group that looks at the case and decides. Think of it as a referee between the railway companies and the people who use them. This is a specialist abbreviation. You will meet it in American business news, transport news, and law, and almost nowhere else. Nobody says it in normal conversation, and it is not something you need for daily English — but if you read about American trains or shipping, it appears constantly. Say it letter by letter: S-T-B. One thing to know: these three letters stand for other things too, in other fields. In medicine, in sport, in company names, STB can mean something completely different. Here it means the American transport board, and the only way to know which one is meant is to look at what the writing is about.