The Collaborative International Dictionary of English v.0.48:

Vidame \Vi*dame"\, n. [F., fr. LL. vice-dominus, fr. L. vice
   instead of + dominus master, lord.] (Fr. Feud. Law)
   One of a class of temporal officers who originally
   represented the bishops, but later erected their offices into
   fiefs, and became feudal nobles.
   [1913 Webster]