Source : Webster's Revised Unabridged Dictionary (1913)

Yankee \Yan"kee\, a.
   Of or pertaining to a Yankee; characteristic of the Yankees.

         The alertness of the Yankee aspect.      --Hawthorne.

   {Yankee clover}. (Bot.) See {Japan clover}, under {Japan}.

Yankee \Yan"kee\, n. [Commonly considered to be a corrupt
   pronunciation of the word English, or of the French word
   Anglais, by the native Indians of America. According to
   Thierry, a corruption of Jankin, a diminutive of John, and a
   nickname given to the English colonists of Connecticut by the
   Dutch settlers of New York. Dr. W. Gordon (``Hist. of the
   Amer. War,'' ed, 1789, vol. i., pp. 324, 325) says it was a
   favorite cant word in Cambridge, Mass., as early as 1713, and
   that it meant excellent; as, a yankee good horse, yankee good
   cider, etc. Cf. Scot yankie a sharp, clever, and rather bold
   woman, and Prov. E. bow-yankees a kind of leggins worn by
   agricultural laborers.]
   A nickname for a native or citizen of New England, especially
   one descended from old New England stock; by extension, an
   inhabitant of the Northern States as distinguished from a
   Southerner; also, applied sometimes by foreigners to any
   inhabitant of the United States.

         From meanness first this Portsmouth Yankey rose, And
         still to meanness all his conduct flows. --Oppression,
                                                  A poem by an
                                                  American
                                                  (Boston,
                                                  1765).

Source : WordNet®

Yankee
     n 1: an American who lives in the North (especially during the
          American Civil War) [syn: {Yank}, {Northerner}]
     2: an American who lives in New England [syn: {New Englander},
        {Yank}]
     3: an American [syn: {Yank}, {Yankee-Doodle}]

Yankee
     adj : used by southerners for an inhabitant of a northern state in
           the United States (especially a Union soldier)