[L. Aqua, water, and ductus, passage.] An artificial channel to convey water for city supply and other pur-poses. The Romans had great stone aqueducts, in some places raised on high arches, in others cut through the hills. Some of these are still in use. Some of the largest of modern aqueducts are the Croton Aqueduct, which conveys water to New York City, and the Cochituate Aqueduct, of Boston, which is fifteen miles long.