The Collaborative International Dictionary of English v.0.48:

Episcopacy \E*pis"co*pa*cy\, n. [See Episcopate.]
   Government of the church by bishops; church government by
   three distinct orders of ministers -- bishops, priests, and
   deacons -- of whom the bishops have an authority superior and
   of a different kind.
   [1913 Webster]

WordNet (r) 3.0 (2006):

episcopacy
    n 1: the collective body of bishops [syn: episcopacy,
         episcopate]

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "episcopacy":
   abbacy, aedileship, archbishopric, archdeaconry, archiepiscopacy,
   archiepiscopate, aristocracy, bishopdom, bishopric, canonicate,
   canonry, cardinalship, chairmanship, chancellery, chancellorate,
   chancellorship, chaplaincy, chaplainship, chiefery, chiefry,
   chieftaincy, chieftainry, chieftainship, consulate, consulship,
   curacy, deaconry, deaconship, deanery, deanship, dictatorship,
   dictature, directorship, emirate, episcopate, governorship,
   headship, hegemony, hierarchy, leadership, lordship, magistracy,
   magistrateship, magistrature, masterdom, mastership, mastery,
   mayoralty, mayorship, metropolitanate, metropolitanship, nobility,
   papacy, pashadom, pashalic, pastorate, pastorship, patriarchate,
   patriarchy, pontificality, pontificate, popedom, popehood,
   popeship, prebend, prebendaryship, prefectship, prefecture,
   prelacy, prelateship, prelature, premiership, presbyterate,
   presbytery, presidency, presidentship, primacy, prime-ministership,
   prime-ministry, princedom, princeship, principality, proconsulate,
   proconsulship, protectorate, protectorship, provostry, provostship,
   rectorate, rectorship, regency, regentship, ruling class,
   seigniory, seneschalship, seneschalsy, sheikhdom, sheriffalty,
   sheriffcy, sheriffdom, shrievalty, supervisorship, suzerainship,
   suzerainty, tribunate, vicariate, vicarship, vizierate,
   viziership



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

EPISCOPACY, eccl. law. A form of government by diocesan bishops; the office
or condition of a bishop.