Source : Webster's Revised Unabridged Dictionary (1913)

Postage \Post"age\, n.
   The price established by law to be paid for the conveyance of
   a letter or other mailable matter by a public post.

   {Postage stamp}, a government stamp required to be put upon
      articles sent by mail in payment of the postage, esp. an
      adhesive stamp issued and sold for that purpose.

Source : WordNet®

postage
     n 1: the charge for mailing something
     2: a token that postal fees have been paid [syn: {postage stamp},
         {stamp}]