Source : Webster's Revised Unabridged Dictionary (1913)

Governess \Gov"ern*ess\, n. [Cf. OF. governeresse. See
   {Governor}.]
   A female governor; a woman invested with authority to control
   and direct; especially, one intrusted with the care and
   instruction of children, -- usually in their homes.

Source : WordNet®

governess
     n : a woman entrusted with the care and supervision of a child
         (especially in a private home)