Source : Webster's Revised Unabridged Dictionary (1913)

Decillion \De*cil"lion\, n. [L. decem ten + the ending of
   million.]
   According to the English notation, a million involved to the
   tenth power, or a unit with sixty ciphers annexed; according
   to the French and American notation, a thousand involved to
   the eleventh power, or a unit with thirty-three ciphers
   annexed. [See the Note under {Numeration}.]