The Collaborative International Dictionary of English v.0.48:

Jersey \Jer"sey\, n.; pl. Jerseys. [From Jersey, the largest
   of the Channel Islands.]
   [1913 Webster]
   1. The finest of wool separated from the rest; combed wool;
      also, fine yarn of wool.
      [1913 Webster]

   2. A kind of knitted jacket; hence, in general, a
      closefitting jacket or upper garment made of an elastic
      fabric (as stockinet).
      [1913 Webster]

   3. One of a breed of cattle in the Island of Jersey. Jerseys
      are noted for the richness of their milk.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Jersey
    n 1: a Mid-Atlantic state on the Atlantic; one of the original
         13 colonies [syn: New Jersey, Jersey, Garden State,
         NJ]
    2: the largest of the Channel Islands [syn: Jersey, island of
       Jersey]
    3: a close-fitting pullover shirt [syn: jersey, T-shirt,
       tee shirt]
    4: a slightly elastic machine-knit fabric
    5: a breed of diary cattle developed on the island of Jersey