Source : Webster's Revised Unabridged Dictionary (1913)

Soutane \Sou`tane"\, n. [F., fr. Sp. sotana, or It. sottana, LL.
   subtana, fr. L. subtus below, beneath, fr. sub under.] (Eccl.
   Costume)
   A close garnment with straight sleeves, and skirts reaching
   to the ankles, and buttoned in front from top to bottom;
   especially, the black garment of this shape worn by the
   clergy in France and Italy as their daily dress; a cassock.

Source : WordNet®

soutane
     n : a long cassock with buttons down the front; worn by Roman
         Catholic priests