The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. A body proprietors, taken collectively.
      [1913 Webster]

   3. (Eccl.) A monk who had reserved goods and effects to
      himself, notwithstanding his renunciation of all at the
      time of profession.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Proprietary \Pro*pri"e*ta*ry\, a. [L. proprietarius.]
   Belonging, or pertaining, to a proprietor; considered as
   property; owned; as, proprietary medicine.
   [1913 Webster]

   Proprietary articles, manufactured articles which some
      person or persons have exclusive right to make and sell.
      --U. S. Statutes.
      [1913 Webster]

WordNet (r) 3.0 (2006):

proprietary
    adj 1: 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]
    n 1: an unincorporated business owned by a single person who is
         responsible for its liabilities and entitled to its profits
         [syn: proprietorship, proprietary]

The Free On-line Dictionary of Computing (19 January 2023):

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 standards, 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]


The Jargon File (version 4.4.7, 29 Dec 2003):

proprietary
 adj.

    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 standards, and thus one that puts the customer
    at the mercy of a vendor able to gouge freely on service and upgrade
    charges after the initial sale has locked the customer in. Often used in
    the phrase “proprietary crap”.

    3. Synonym for closed-source or non-free, e.g. software issued without
    license rights permitting the public to independently review, develop and
    redistribute it.

    Proprietary software should be distinguished from commercial software. It
    is possible for software to be commercial (that is, intended to make a
    profit for the producers) without being proprietary. The reverse is also
    possible, for example in binary-only freeware.