Source : Webster's Revised Unabridged Dictionary (1913)

Dun \Dun\, a. [AS. dunn. of Celtic origin; cf. W. dwn, Ir. &
   Gael. donn.]
   Of a dark color; of a color partaking of a brown and black;
   of a dull brown color; swarthy.

         Summer's dun cloud comes thundering up.  -- Pierpont.

         Chill and dun Falls on the moor the brief November day.
                                                  --Keble.

   {Dun crow} (Zo["o]l.), the hooded crow; -- so called from its
      color; -- also called {hoody}, and {hoddy}.

   {Dun diver} (Zo["o]l.), the goosander or merganser.