Hypertext Webster Gateway: "Viaduct"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
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}.
From WordNet (r) 1.7 (wn)
viaduct
n : bridge consisting of a series of arches supported by piers
used to carry a road (or railroad) over a valley
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