noun (n)

• a sign posted in a public place as an advertisement(noun.communication)

  Synonym:
  bill, card, notice, placard, poster
  

  source: wordnet30
• (bookkeeping) a listing on the company's records(noun.communication)

  Example:
  The posting was made in the cash account.
  

  source: wordnet30
• the transmission of a letter(noun.act)

  Synonym:
  mailing
  

  source: wordnet30
• The act of traveling post.(noun)

  source: webster1913