aqueduct

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A pipe or channel designed to transport water from a remote source, usually by gravity.
2. n. A bridgelike structure supporting a conduit or canal passing over a river or low ground.
3. n. Anatomy A channel or passage in an organ or a body part, especially such a channel for conveying fluid.

Century Dictionary and Cyclopedia

1. n. A conduit or channel for conducting water from one place to another. More particularly applied to structures of masonry and tunneling for the conducting of water from distant sources to large cities through tubular conduits. Aqueducts were extensively used in the Roman empire, and many of these ancient structures still remain. They were constructed of stone or wood, sometimes tunneled through hills and carried over valleys and rivers on arches, much of the labor upon them being uselessly expended, from a mistaken idea of the necessity of a perfectly level course. The aqueduct of Segovia, originally built by the Romans, has 159 arches, is in some parts built in two tiers 100 feet or more in height, and is an admirable monument of ancient engineering. One of the most remarkable aqueducts of modern times is that of Marseilles, to which city it conveys the waters of the river Durance from a distance of about 58 miles, of which 10 miles consists of tunnels, and a considerable portion is traversed by means of viaducts of great height and length. This aqueduct was built between 1839 and 1847, and supplies water in such abundance that the environs of Marseilles, formerly extremely arid, have become a garden from the plentiful irrigation which is now possible.
2. n. In anatomy, same as aquœductus.

Wiktionary

1. n. An artificial channel that is constructed to convey water from one location to another.
2. n. A structure carrying water over a river or depression, especially in regards to ancient aqueducts.

GNU Webster's 1913

1. n. A conductor, conduit, or artificial channel for conveying water, especially one for supplying large cities with water.
2. n. (Anat.) A canal or passage.

WordNet 3.0

1. n. a conduit that resembles a bridge but carries water over a valley