Source : Webster's Revised Unabridged Dictionary (1913)

Steganography \Steg`a*nog"ra*phy\, n. [Gr. ? covered (fr. ? to
   cover closely) + -graphy.]
   The art of writing in cipher, or in characters which are not
   intelligible except to persons who have the key;
   cryptography.

Source : Free On-Line Dictionary of Computing

steganography
     
         Hiding a secret message within a larger one in such
        a way that others can not discern the presence or contents of
        the hidden message.  For example, a message might be hidden
        within an {image} by changing the {least significant bits} to
        be the message bits.
     
        [{Chaffing and Winnowing: Confidentiality without Encryption,
        Ronald L. Rivest, MIT Lab for Computer Science, 1998-03-22
        (http://theory.lcs.mit.edu/~rivest/chaffing.txt)}].
     
        (1998-07-13)