mailbag

from WordNet (r) 3.0 (2006)

mailbag
    n 1: pouch used in the shipment of mail [syn: {mailbag}, {mail
         pouch}]
    2: letter carrier's shoulder bag; "in Britain they call a
       mailbag a postbag" [syn: {mailbag}, {postbag}]

from The Collaborative International Dictionary of English v.0.48

mailbag \mail"bag`\, mail bag \mail bag\n.
   A bag in which mailed matter is conveyed or shipped under
   public authority.

   Syn: mail pouch.
        [WordNet 1.5]

   2. A letter carrier's shoulder bag; as, in England they call
      a mailbag a postbag.

   Syn: postbag.
        [WordNet 1.5] mailboat