WordNet (r) 3.0 (2006):

public utility
    n 1: a company that performs a public service; subject to
         government regulation [syn: utility, public utility,
         public utility company, public-service corporation]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "public utility":
   Aktiengesellschaft, aktiebolag, body corporate, business,
   business establishment, cartel, chamber of commerce, combine,
   commercial enterprise, compagnie, company, concern, conglomerate,
   conglomerate corporation, consolidating company, consortium,
   copartnership, corporate body, corporation,
   diversified corporation, enterprise, firm, holding company, house,
   industry, joint-stock association, joint-stock company,
   operating company, partnership, plunderbund, pool, stock company,
   syndicate, trade association, trust, utility