Sim•plon(sim′plon; Fr. san plôn′),USA pronunciationn.
Place Namesa mountain pass in S Switzerland, in the Lepontine Alps: crossed by a carriage road constructed 1800–06 on Napoleon's orders. 6592 ft. (2010 m) high.
Place Namesa tunnel between Switzerland and Italy, NE of the Simplon Pass: longest tunnel in the world. 12¼ mi. (20 km) long.