'Viaduct' definitions:

Definition of 'viaduct'

From: WordNet
noun
Bridge consisting of a series of arches supported by piers used to carry a road (or railroad) over a valley

Definition of 'Viaduct'

From: GCIDE
  • Viaduct \Vi`a*duct\, n. [L. via a way + -duct, as in aqueduct: cf. F. viaduc. See Via, and Aqueduct.] A structure of considerable magnitude, usually with arches or supported on trestles, for carrying a road, as a railroad, high above the ground or water; a bridge; especially, one for crossing a valley or a gorge. Cf. Trestlework. [1913 Webster]