Source : Webster's Revised Unabridged Dictionary (1913)

Marquess \Mar"quess\, n. [Cf. Sp. marques. See {Marquis}.]
   A marquis.

   {Lady marquess}, a marchioness. [Obs.] --Shak.

Source : WordNet®

marquess
     n 1: nobleman (in various countries) ranking above a count [syn:
          {marquis}]
     2: a British peer ranking below a duke and above an earl