(n) a number of covers or arches familiar with carry a road or railroad over a wide valley or over other roadways or railroads.
(n) A bridge with a few spans that carries roadway or train traffic over a valley or other obstacles.
(n) A structure of substantial magnitude, often with arches or supported on trestles, to carry a road, as a railroad, high above the ground or water; a bridge; specially, one for crossing a valley or a gorge. Cf. trestlework.
viaduct in Community Dictionary
Short the Alaskan means Viaduct, the double-deck freeway that lines Seattle's waterfront. The Viaduct is gradually crumbling into a million pieces due to quake harm, and certainly will probably be replaced next few years. by MichaelReport definition