[1] : The Collaborative International Dictionary of English v.0.48

postal \post"al\, a. cf. f. postal.
   belonging to the post office or mail service; as, postal
   arrangements; postal authorities.
   1913 webster

   postal card, or post card, a card used for transmission
      of messages through the mails, at a lower rate of postage
      than a sealed letter; also called postcard. such cards
      are sold by the government with postage already paid, or
      by private vendors without a postage stamp. the message is
      written on one side of the card, and the address on the
      other.

   postal money order. see money order, under money.

   postal note, an order payable to bearer, for a sum of money
      in the united states less than five dollars under
      existing law, issued from one post office and payable at
      another specified office.

   postal union, a union for postal purposes entered into by
      the most important powers, or governments, which have
      agreed to transport mail matter through their several
      territories at a stipulated rate.
      1913 webster
see also:
postal card post card postcard postal money order money order money 
postal note postal union 

[2] : WordNet (r) 2.0

postal
     adj : of or relating to the system for delivering mail; "postal
           delivery"

Postal >> P Words
Postal, definition of term: Postal
postal_pag1.html

Postal Code >> P Words
Postal Code, definition of term: Postal Code
postal+code_pag1.html