A chain of interconnected special cars, usu. with 2-4 axles, built to run on rails. Pushed or pulled by a locomotive, which is powered either by steam, diesel or electricity. Quite common in Europe and Japan as a means of mass transportation, touted as an alternative to much more energy consuming and polluting vehicles such as cars and airplanes.
Modern designs such as the French TGV or the German ICE achieve speeds that make them a faster, more punctual alternative to airplanes for distances in the 500-2000 kilometre area. Drawbacks are high infrastructure and maintenance costs. Only suitable for well-developped societies with high population density. Even Americans will eventually grasp their benefits.