The Collaborative International Dictionary of English v.0.48:

Domain \Do*main"\, n. [F. domaine, OF. demaine, L. dominium,
   property, right of ownership, fr. dominus master, owner. See
   Dame, and cf Demesne, Dungeon.]
   1. Dominion; empire; authority.
      [1913 Webster]

   2. The territory over which dominion or authority is exerted;
      the possessions of a sovereign or commonwealth, or the
      like. Also used figuratively. [WordNet sense 2]
      [1913 Webster]

            The domain of authentic history.      --E. Everett.
      [1913 Webster]

            The domain over which the poetic spirit ranges. --J.
                                                  C. Shairp.
      [1913 Webster]

   3. Landed property; estate; especially, the land about the
      mansion house of a lord, and in his immediate occupancy;
      demesne. [WordNet sense 2] --Shenstone.
      [1913 Webster]

   4. (Law) Ownership of land; an estate or patrimony which one
      has in his own right; absolute proprietorship; paramount
      or sovereign ownership.
      [1913 Webster]

   5. (Math.) the set of values which the independent variable
      of a function may take. Contrasted to range, which is
      the set of values taken by the dependent variable.
      [WordNet sense 3]
      [PJC]

   6. (Math.) a connected set of points, also called a region.
      [PJC]

   7. (Physics) a region within a ferromagnetic material,
      composed of a number of atoms whose magnetic poles are
      pointed in the same direction, and which may move together
      in a coordinated manner when disturbed, as by heating. The
      direction of polarity of adjacent domains may be
      different, but may be aligned by a strong external
      magnetic field.
      [PJC]

   8. (Computers) an address within the internet computer
      network, which may be a single computer, a network of
      computers, or one of a number of accounts on a multiuser
      computer. The domain specifies the location (host
      computer) to which communications on the internet are
      directed. Each domain has a corresponding 32-bit number
      usually represented by four numbers separated by periods,
      as 128.32.282.56. Each domain may also have an
      alphabetical name, usually composed of a name plus an
      extension separated by a period, as worldsoul.org; the
      alphabetical name is referred to as a domain name.
      [PJC]

   9. (Immunology) the three-dimensional structure within an
      immunoglobulin which is formed by one of the homology
      regions of a heavy or light chain. --Dict. Sci. Tech.
      [PJC]

   10. the field of knowledge, expertise, or interest of a
       person; as, he had a limited domain of discourse; I can't
       comment on that, it's outside my domain. [WordNet sense
       5]

   Syn: domain, realm, field, area. [PJC]

   11. a particular environment or walk of life. [WordNet sense
       1]

   Syn: sphere, domain, area, orbit, field, arena. [PJC]

   12. people in general; especially a distinctive group of
       people with some shared interest. [WordNet sense 4]

   Syn: world, domain. [PJC]

   Public domain,

   1. the territory belonging to a State or to the general
      government; public lands. [U.S.]

   2. the situation or status of intellectual property which is
      not protected by copyright, patent or other restriction on
      use. Anything

   in the public domain may be used by anyone without
      restriction. The effective term of force of copyrights and
      patents are limited by statute, and after the term
      expires, the writings and inventions thus protected go
      into the public domain and are free for use by all.

   Right of eminent domain, that superior dominion of the
      sovereign power over all the property within the state,
      including that previously granted by itself, which
      authorizes it to appropriate any part thereof to a
      necessary public use, reasonable compensation being made.
      [1913 Webster]

WordNet (r) 3.0 (2006):

domain
    n 1: a particular environment or walk of life; "his social
         sphere is limited"; "it was a closed area of employment";
         "he's out of my orbit" [syn: sphere, domain, area,
         orbit, field, arena]
    2: territory over which rule or control is exercised; "his
       domain extended into Europe"; "he made it the law of the
       land" [syn: domain, demesne, land]
    3: (mathematics) the set of values of the independent variable
       for which a function is defined [syn: domain, domain of a
       function]
    4: people in general; especially a distinctive group of people
       with some shared interest; "the Western world" [syn: world,
       domain]
    5: the content of a particular field of knowledge [syn:
       knowledge domain, knowledge base, domain]

Moby Thesaurus II by Grady Ward, 1.0:

132 Moby Thesaurus words for "domain":
   academic discipline, academic specialty, acres, ally, ambit,
   animal kingdom, applied science, archduchy, archdukedom, area,
   arena, art, bailiwick, beat, body politic, border, borderland,
   buffer state, captive nation, chain of being, champaign,
   chattels real, chieftaincy, chieftainry, circle, circuit,
   city-state, class structure, colony, commonweal, commonwealth,
   concern, country, county, demesne, department,
   department of knowledge, discipline, dominion, duchy, dukedom,
   earldom, empery, empire, establishment, field, field of inquiry,
   field of study, free city, grand duchy, grounds, hemisphere,
   hierarchy, honor, judicial circuit, jurisdiction, kingdom, land,
   landed property, lands, lot, lots, mandant, mandate,
   mandated territory, mandatee, mandatory, manor, march, messuage,
   mineral kingdom, nation, nationality, natural hierarchy,
   natural science, ology, orb, orbit, pale, parcel, pecking order,
   plat, plot, polis, polity, possession, power, power structure,
   praedium, precinct, principality, principate, property,
   protectorate, province, puppet government, puppet regime,
   pure science, pyramid, quadrat, real estate, real property, realm,
   realty, republic, round, satellite, science, seneschalty,
   settlement, social science, sovereign nation, speciality,
   specialization, specialty, sphere, state, study, subdiscipline,
   sultanate, superpower, technicology, technics, technology,
   tenements, terrain, territory, toft, toparchia, toparchy,
   vegetable kingdom, walk



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

DOMAIN
       Distributed Operating Multi Access Interactive Network (Apollo,
DOMAIN)


The Free On-line Dictionary of Computing (30 December 2018):

domain

   1.  A group of computers whose fully qualified
   domain names (FQDN) share a common suffix, the "domain name".

   The Domain Name System maps hostnames to Internet
   address using a hierarchical namespace where each level in
   the hierarchy contributes one component to the FQDN.  For
   example, the computer foldoc.doc.ic.ac.uk is in the
   doc.ic.ac.uk domain, which is in the ic.ac.uk domain, which is
   in the ac.uk domain, which is in the uk top-level domain.

   A domain name can contain up to 67 characters including the
   dots that separate components.  These can be letters, numbers
   and hyphens.

   2. An administrative domain is something to do with routing.

   3. Distributed Operating Multi Access Interactive Network.

   4.  In the theory of functions, the set of
   argument values for which a function is defined.

   See domain theory.

   5.  A specific phase of the software life cycle
   in which a developer works.  Domains define developers' and
   users' areas of responsibility and the scope of possible
   relationships between products.

   6. The subject or market in which a piece of software is
   designed to work.

   (2007-10-01)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

DOMAIN. It signifies sometimes, dominion, territory governed - sometimes,
possession, estate - and sometimes, land about the mansion house of a lord.
By domain is also understood the right to dispose at our pleasure of what
belongs to us.
     2. A distinction, has been made between property and domain. The former
is said to be that quality which is conceived to be in the thing itself,
considered as belonging to such or such person, exclusively of all others.
By the latter is understood that right which the owner has of disposing of
the thing. Hence domain and property are said to be correlative terms; the
one is the active right to dispose, the other a passive quality which
follows the thing, and places it at the disposition of the owner. 3 Toull.
n. 8 3. But this distinction is too subtle for practical use. Puff. Droit de
la Nature et des Gens, loi 4, c. 4, Sec. 2. Vide 1 B1. Com. 105, 106; 1
Bouv. Inst. n. 456; Clef des Lois Rom. h.t.; Domat, h.t.; 1 Hill. Ab. 24;
2 Hill. Ab. 237; and Demesne as Of fee; Property; Things.