The Collaborative International Dictionary of English v.0.48:

Establishment \Es*tab"lish*ment\, n. [Cf. OF. establissement, F.
   ['e]tablissement.]
   1. The act of establishing; a ratifying or ordaining;
      settlement; confirmation.
      [1913 Webster]

   2. The state of being established, founded, and the like;
      fixed state.
      [1913 Webster]

   3. That which is established; as:
      (a) A form of government, civil or ecclesiastical;
          especially, a system of religion maintained by the
          civil power; as, the Episcopal establishment of
          England.
      (b) A permanent civil, military, or commercial, force or
          organization.
      (c) The place in which one is permanently fixed for
          residence or business; residence, including grounds,
          furniture, equipage, etc.; with which one is fitted
          out; also, any office or place of business, with its
          fixtures; that which serves for the carrying on of a
          business; as, to keep up a large establishment; a
          manufacturing establishment.
          [1913 Webster]

                Exposing the shabby parts of the establishment.
                                                  --W. Irving.
          [1913 Webster]

   Establishment of the port (Hydrography), a datum on which
      the tides are computed at the given port, obtained by
      observation, viz., the interval between the moon's passage
      over the meridian and the time of high water at the port,
      on the days of new and full moon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

establishment
    n 1: the act of forming or establishing something; "the
         constitution of a PTA group last year"; "it was the
         establishment of his reputation"; "he still remembers the
         organization of the club" [syn: constitution,
         establishment, formation, organization,
         organisation]
    2: an organization founded and united for a specific purpose
       [syn: institution, establishment]
    3: the persons (or committees or departments etc.) who make up a
       body for the purpose of administering something; "he claims
       that the present administration is corrupt"; "the governance
       of an association is responsible to its members"; "he quickly
       became recognized as a member of the establishment" [syn:
       administration, governance, governing body,
       establishment, brass, organization, organisation]
    4: a public or private structure (business or governmental or
       educational) including buildings and equipment for business
       or residence
    5: any large organization
    6: (ecology) the process by which a plant or animal becomes
       established in a new habitat [syn: establishment, ecesis]
    7: the cognitive process of establishing a valid proof [syn:
       establishment, validation]

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "Establishment":
   John Bull, Rasputin, Svengali, Uncle Sam, VIP, Washington,
   Whitehall, access, bad influence, baron, big gun, big man,
   big name, big wheel, bigwig, brass, brass hat, bureaucracy,
   celebrity, court, dignitary, dignity, directorate, elder,
   eminence grise, father, figure, five-percenter, friend at court,
   good influence, gray eminence, great man, heavyweight, hidden hand,
   hierarchy, higher echelons, higher-ups, important person,
   influence, influence peddler, influencer, ingroup, interests, key,
   kingmaker, lion, lobby, lobbyist, lords of creation, magnate,
   man of influence, man of mark, management, manipulator, ministry,
   mogul, nabob, name, notability, notable, officialdom, open sesame,
   panjandrum, person of renown, personage, personality,
   pillar of society, power, power elite, powers that be, prelacy,
   pressure group, ruling circle, ruling class, ruling classes,
   sachem, sinister influence, somebody, something, special interests,
   special-interest group, the Crown, the Establishment,
   the administration, the authorities, the government, the great,
   the ingroup, the interests, the people upstairs, the power elite,
   the power structure, the top, them, they, top brass, top people,
   tycoon, very important person, wheeler-dealer, wire-puller,
   worthy



Moby Thesaurus II by Grady Ward, 1.0:

207 Moby Thesaurus words for "establishment":
   A, Old Guard, absolute indication, agency, alpha, anchorage,
   animal kingdom, architecture, aristocracy, ascertainment,
   assurance, atelier, barbershop, barons, beauty parlor, beauty shop,
   beginning, bench, blast-off, boutique, building, burden of proof,
   business, butcher shop, certification, chain of being, chain store,
   check, checking, class structure, co-op, collation, colonization,
   commencement, company, concern, concession, conclusive evidence,
   confirmation, constitution, construct, construction, cooperative,
   corporation, countinghouse, country store, cream, creation,
   cutting edge, damning evidence, dawn, deep-rootedness,
   deep-seatedness, demonstration, department store, desk,
   determination, dime store, discount house, discount store, domain,
   edge, edifice, effectuation, elite, embedment, emporium, ensuring,
   enterprise, entrenchment, erection, fabric, facility, firm,
   five-and-ten, fixation, fixedness, fixity, fixture, flying start,
   formation, foundation, founding, fresh start, general store,
   hierarchy, house, implantation, inauguration, inception,
   incontrovertible evidence, indisputable evidence, infixion,
   initiation, installation, installment, institute, institution,
   investiture, inveteracy, ironclad proof, jump-off, kick-off,
   kingdom, leading edge, lodgment, loft, lords of creation, magasin,
   mail-order house, market, mart, materialization, mineral kingdom,
   mooring, natural hierarchy, new departure, nobility, office,
   oncoming, onset, onus, onus probandi, opening, organization,
   origin, origination, outbreak, outfit, outset, overlapping,
   packaged house, parlor, pecking order, peopling, pile, plantation,
   population, post, power elite, power structure, prefab,
   prefabrication, proof, pyramid, realization, realm, reassurance,
   reassurement, retail store, ruling circles, ruling class,
   running start, salon, send-off, setting in motion, setting-up,
   settlement, settling, shop, skyscraper, square one, stabilization,
   start, start-off, starting point, store, structure, studio,
   substantiation, supermarket, superstructure, sure sign, sweatshop,
   take-off, the Church, the Establishment, the administration,
   the authorities, the best, the best people, the brass,
   the government, the power structure, top people, tower,
   trading post, unmistakable sign, upper class, upper crust,
   validation, variety shop, variety store, vegetable kingdom,
   verification, warehouse, wareroom, wholesale house, work site,
   work space, workbench, workhouse, working space, workplace,
   workroom, workshop, worktable