The Collaborative International Dictionary of English v.0.48:

advertising \advertising\ n.
   1. a communication publicly promoting some product or
      service.

   Syn: ad, advertisement, advert
        [WordNet 1.5]

   2. 1 the business of advertising; the activity engaged in by
      professional publicists for pay.

   Syn: advertizing, publicizing, the advertising profession,
        the advertising industry
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Advertise \Ad`ver*tise"\ (?; 277), v. t. [imp. & p. p.
   Advertised; p. pr. & vb. n. Advertising.] [F. avertir,
   formerly also spelt advertir, to warn, give notice to, L.
   advertere to turn to. The ending was probably influenced by
   the noun advertisement. See Advert.]
   To give notice to; to inform or apprise; to notify; to make
   known; hence, to warn; -- often followed by of before the
   subject of information; as, to advertise a man of his loss.
   [Archaic]
   [1913 Webster]

         I will advertise thee what this people shall do. --Num.
                                                  xxiv. 14.
   [1913 Webster]

   4. To give public notice of; to announce publicly, esp. by a
      printed notice; as, to advertise goods for sale, a lost
      article, the sailing day of a vessel, a political meeting.
      [1913 Webster]

   Syn: To apprise; inform; make known; notify; announce;
        proclaim; promulgate; publish.
        [1913 Webster]

WordNet (r) 3.0 (2006):

advertising
    n 1: a public promotion of some product or service [syn: ad,
         advertisement, advertizement, advertising,
         advertizing, advert]
    2: the business of drawing public attention to goods and
       services [syn: advertising, publicizing]