The Collaborative International Dictionary of English v.0.48:

Yacht \Yacht\ (y[o^]t), n. [D. jagt, jacht; perhaps properly, a
   chase, hunting, from. jagen to chase, hunt, akin to G. jagen,
   OHG. jag[=o]n, of uncertain origin; or perhaps akin to OHG.
   g[=a]hi quick, sudden (cf. Gay).] (Naut.)
   A light and elegantly furnished vessel, used either for
   private parties of pleasure, or as a vessel of state to
   convey distinguished persons from one place to another; a
   seagoing vessel used only for pleasure trips, racing, etc.
   [1913 Webster]

   Yacht measurement. See the Note under Tonnage, 4.
      [1913 Webster]