The Collaborative International Dictionary of English v.0.48:

Cooperative \Co*["o]p"er*a*tive\, a.
   Operating jointly to the same end.
   [1913 Webster]

   Cooperative society, a society established on the principle
      of a joint-stock association, for the production of
      commodities, or their purchase and distribution for
      consumption, or for the borrowing and lending of capital
      among its members.

   Cooperative store, a store established by a cooperative
      society, where the members make their purchases and share
      in the profits or losses.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cooperative
    adj 1: involving the joint activity of two or more; "concerted
           action"; "the conjunct influence of fire and strong
           wind"; "the conjunctive focus of political opposition";
           "a cooperative effort"; "a united effort"; "joint
           military activities" [syn: concerted, conjunct,
           conjunctive, cooperative]
    2: done with or working with others for a common purpose or
       benefit; "a cooperative effort" [ant: uncooperative]
    3: willing to adjust to differences in order to obtain agreement
       [syn: accommodative, cooperative]
    n 1: a jointly owned commercial enterprise (usually organized by
         farmers or consumers) that produces and distributes goods
         and services and is run for the benefit of its owners [syn:
         cooperative, co-op]
    2: an association formed and operated for the benefit of those
       using it

Moby Thesaurus II by Grady Ward, 1.0:

230 Moby Thesaurus words for "cooperative":
   Bund, Rochdale cooperative, accompanying, accordant, acquiescent,
   affirmative, agreeable, agreeing, alacritous, alliance, amenable,
   amicable, answerable, ardent, assemblage, associate, associated,
   association, at one, at one with, axis, band, beneficent,
   benevolent, benign, benignant, bloc, body, boutique, chain store,
   co-op, coacting, coactive, coadjutant, coadjuvant, coadunate,
   coalition, coefficient, coexistent, coexisting, coherent,
   coincident, coinciding, collaborative, collective, collectivist,
   collectivistic, college, collusive, combination, combine, combined,
   combining, commensal, commensurate, common, common market,
   communal, communalist, communalistic, communist, communistic,
   communitarian, commutual, compatible, compliant, concerted,
   concession, concomitant, concordant, concurrent, concurring,
   confederacy, confederation, conformable, congenial, congruent,
   congruous, conjoint, conniving, consentaneous, consentient,
   consenting, consilient, consistent, consonant, conspiratorial,
   consumer cooperative, content, cooperant, cooperating,
   cooperative society, coordinate, corps, correspondent,
   corresponding, council, countinghouse, country store, coworking,
   credit union, customs union, department store, dime store,
   discount house, discount store, disposed, docile, eager,
   economic community, ecumenic, emporium, en rapport, enthusiastic,
   equivalent, establishment, fain, favorable, favorably disposed,
   favorably inclined, federation, fellow, five-and-ten, forward,
   free trade area, friendly, game, gang, general, general store,
   group, grouping, harmonious, harmonized, house, in accord,
   in agreement, in common, in rapport, in sync, in synchronization,
   in the mind, in the mood, inaccordance, inclined, inharmony, joint,
   kind, kindly, kindly-disposed, league, like-minded, machine,
   magasin, mail-order house, market, mart, meeting, minded, mob,
   mutual, neighborly, noncompetitive, of a piece, of like mind,
   of one mind, on all fours, parasitic, partnership, pliant,
   political machine, popular, positive, post, predisposed, prompt,
   prone, propitious, proportionate, public, quick, ready,
   ready and willing, receptive, reciprocal, reconcilable, responsive,
   retail store, ring, salon, saprophytic, self-consistent, shop,
   social, socialistic, societal, society, store, supermarket,
   symbiotic, synchronized, synchronous, synergetic, synergic,
   synergistic, tractable, trading post, unanimous, uncompetitive,
   uniform, union, unisonant, unisonous, united, uniting,
   variety shop, variety store, warehouse, wareroom, well-affected,
   well-disposed, well-inclined, well-intentioned, well-meaning,
   well-meant, wholesale house, willed, willing, willinghearted,
   zealous