The Collaborative International Dictionary of English v.0.48:

Wain \Wain\, n. [OE. wain, AS. w[ae]gn; akin to D. & G. wagen,
   OHG. wagan, Icel. & Sw. vagn, Dan. vogn, and E. way. ????.
   See Way, Weigh, and cf. Wagon.]
   [1913 Webster]
   1. A four-wheeled vehicle for the transportation of goods,
      produce, etc.; a wagon.
      [1913 Webster]

            The wardens see nothing but a wain of hay.
                                                  --Jeffrey.
      [1913 Webster]

            Driving in ponderous wains their household goods to
            the seashore.                         --Longfellow.
      [1913 Webster]

   2. A chariot. [Obs.]
      [1913 Webster]

   The Wain. (Astron.) See Charles's Wain, in the
      Vocabulary.

   Wain rope, a cart rope. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Wain
    n 1: English writer (1925-1994) [syn: Wain, John Wain, John
         Barrington Wain]
    2: a group of seven bright stars in the constellation Ursa Major
       [syn: Big Dipper, Dipper, Plough, Charles's Wain,
       Wain, Wagon]
    3: large open farm wagon