The Collaborative International Dictionary of English v.0.48:

Commercial \Com*mer"cial\, a. [Cf. F. commercial.]
   Of or pertaining to commerce; carrying on or occupied with
   commerce or trade; mercantile; as, commercial advantages;
   commercial relations. "Princely commercial houses."
   --Macaulay.
   [1913 Webster]

   Commercial college, a school for giving instruction in
      commercial knowledge and business.

   Commercial law. See under Law.

   Commercial note paper, a small size of writing paper,
      usually about 5 by 71/2 or 8 inches.

   Commercial paper, negotiable paper given in due course of
      business. It includes bills of exchange, promissory notes,
      bank checks, etc.

   Commercial traveler, an agent of a wholesale house who
      travels from town to town to solicit orders.

   Syn: See Mercantile.
        [1913 Webster]

WordNet (r) 3.0 (2006):

commercial
    adj 1: connected with or engaged in or sponsored by or used in
           commerce or commercial enterprises; "commercial trucker";
           "commercial TV"; "commercial diamonds" [ant:
           noncommercial]
    2: of or relating to commercialism; "a commercial attache";
       "commercial paper"; "commercial law"
    3: of the kind or quality used in commerce; average or inferior;
       "commercial grade of beef"; "commercial oxalic acid" [syn:
       commercial, commercial-grade]
    n 1: a commercially sponsored ad on radio or television [syn:
         commercial, commercial message]