The Collaborative International Dictionary of English v.0.48:

Duke \Duke\ (d[=u]k) v. i.
   To play the duke. [Poetic]
   [1913 Webster]

         Lord Angelo dukes it well in his absence. -- Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

duke \duke\ (d[=u]k) v. t.
   To beat with the fists. [slang]
   [PJC]

   to duke it out to fight; -- usually implying, to fight with
      the fists; to settle a dispute by fighting with the fists.
      See duke, n. sense 4.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Duke \Duke\ (d[=u]k), n. [F. duc, fr. L. dux, ducis, leader,
   commander, fr. ducere to lead; akin to AS. te['o]n to draw;
   cf. AS. heretoga (here army) an army leader, general, G.
   herzog duke. See Tue, and cf. Doge, Duchess, Ducat,
   Duct, Adduce, Deduct.]
   1. A leader; a chief; a prince. [Obs.]
      [1913 Webster]

            Hannibal, duke of Carthage.           --Sir T.
                                                  Elyot.
      [1913 Webster]

            All were dukes once, who were "duces" -- captains or
            leaders of their people.              --Trench.
      [1913 Webster]

   2. In England, one of the highest order of nobility after
      princes and princesses of the royal blood and the four
      archbishops of England and Ireland.
      [1913 Webster]

   3. In some European countries, a sovereign prince, without
      the title of king.
      [1913 Webster]

   4. pl. The fists; as, put up your dukes. [slang]
      [PJC]

   Duke's coronet. See Illust. of Coronet.

   To dine with Duke Humphrey, to go without dinner. See under
      Dine.
      [1913 Webster]

WordNet (r) 3.0 (2006):

duke
    n 1: a British peer of the highest rank
    2: a nobleman (in various countries) of high rank

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "duke":
   Brahman, archduke, aristocrat, armiger, baron, baronet, blue blood,
   count, daimio, earl, esquire, gentleman, grand duke, grandee,
   hidalgo, lace-curtain, laird, landgrave, lord, lordling, magnate,
   magnifico, margrave, marquis, noble, nobleman, optimate, palsgrave,
   patrician, peer, seigneur, seignior, silk-stocking, squire, swell,
   thoroughbred, upper-cruster, viscount, waldgrave



Easton's 1897 Bible Dictionary:

Duke
   derived from the Latin dux, meaning "a leader;" Arabic, "a
   sheik." This word is used to denote the phylarch or chief of a
   tribe (Gen. 36:15-43; Ex. 15:15; 1 Chr. 1:51-54).