Source : Webster's Revised Unabridged Dictionary (1913)

Proprietary \Pro*pri"e*ta*ry\, a. [L. proprietarius.]
   Belonging, or pertaining, to a proprietor; considered as
   property; owned; as, proprietary medicine.

   {Proprietary articles}, manufactured articles which some
      person or persons have exclusive right to make and sell.
      --U. S. Statutes.

Proprietary \Pro*pri"e*ta*ry\, n.; pl. {Proprietaries}. [L.
   proprietarius: cf. F. propri['e]taire. See {Propriety}, and
   cf. {Proprietor}.]
   1. A proprietor or owner; one who has exclusive title to a
      thing; one who possesses, or holds the title to, a thing
      in his own right. --Fuller.

   2. A body proprietors, taken collectively.

   3. (Eccl.) A monk who had reserved goods and effects to
      himself, notwithstanding his renunciation of all at the
      time of profession.

Source : WordNet®

proprietary
     adj : protected by trademark or patent or copyright; made or
           produced or distributed by one having exclusive rights;
           "`Tylenol' is a proprietary drug of which
           `acetaminophen' is the generic form" [ant: {nonproprietary}]

proprietary
     n : an unincorporated business owned by a single person who is
         responsible for its liabilities and entitled to its
         profits [syn: {proprietorship}]

Source : Free On-Line Dictionary of Computing

proprietary
     
        1. In {marketroid}-speak, superior; implies a product imbued
        with exclusive magic by the unmatched brilliance of the
        company's own hardware or software designers.
     
        2. In the language of hackers and users, inferior; implies a
        product not conforming to {open-systems} {standard}s, and thus
        one that puts the customer at the mercy of a vendor who can
        inflate service and upgrade charges after the initial sale has
        locked the customer in.
     
        [{Jargon File}]