Source : Webster's Revised Unabridged Dictionary (1913)

Duct \Duct\, n. [L. ductus a leading, conducting, conduit, fr.
   ducere, ductum, to lead. See {Duke}, and cf. {Douche}.]
   1. Any tube or canal by which a fluid or other substance is
      conducted or conveyed.

   2. (Anat.) One of the vessels of an animal body by which the
      products of glandular secretion are conveyed to their
      destination.

   3. (Bot.) A large, elongated cell, either round or prismatic,
      usually found associated with woody fiber.

   Note: Ducts are classified, according to the character of the
         surface of their walls, or their structure, as annular,
         spiral, scalariform, etc.

   4. Guidance; direction. [Obs.] --Hammond.

Source : WordNet®

duct
     n 1: a bodily passage or tube lined with epithelial cells and
          conveying a secretion or other substance; "the tear duct
          was obstructed"; "the alimentary canal"; "poison is
          released through a channel in the snake's fangs" [syn: {epithelial
          duct}, {canal}, {channel}]
     2: a continuous tube formed by a row of elongated cells lacking
        intervening end walls
     3: an enclosed conduit for a fluid