The Collaborative International Dictionary of English v.0.48:

Vedette \Ve*dette"\, n. [F. vedette, It. vedetta, for veletta
   (influenced by vedere to see, L. videre), from It. veglia
   watch, L. vigilia. See Vigil.]
   A sentinel, usually on horseback, stationed on the outpost of
   an army, to watch an enemy and give notice of danger; a
   vidette.
   [1913 Webster]