The Collaborative International Dictionary of English v.0.48:

Bailiwick \Bail"i*wick\, n. [Bailie, bailiff + wick a village.]
   (Law)
   The precincts within which a bailiff has jurisdiction; the
   limits of a bailiff's authority.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bailiwick
    n 1: the area over which a bailiff has jurisdiction
    2: a branch of knowledge; "in what discipline is his
       doctorate?"; "teachers should be well trained in their
       subject"; "anthropology is the study of human beings" [syn:
       discipline, subject, subject area, subject field,
       field, field of study, study, bailiwick]

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "bailiwick":
   Kreis, ambit, archbishopric, archdiocese, arena, arrondissement,
   beat, bishopric, border, borderland, borough, bureau, canton,
   champaign, circle, circuit, city, commissariat, commune,
   congressional district, constablery, constablewick, constabulary,
   constituency, county, demesne, departement, department, diocese,
   district, domain, dominion, duchy, electoral district, electorate,
   field, footing, government, hamlet, hemisphere, hundred,
   judicial circuit, jurisdiction, magistracy, march, metropolis,
   metropolitan area, ministry, municipality, neighborhood, oblast,
   office, okrug, orb, orbit, pale, parish, place, precinct,
   principality, province, quarter, realm, region, riding, round,
   secretariat, sheriffalty, sheriffwick, shire, shrievalty, soke,
   sphere, sphere of influence, stake, stamping ground, state,
   terrain, territory, town, township, turf, vantage, village, walk,
   wapentake, ward



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

BAILIWICK. The district over which a sheriff has jurisdiction; it signifies
also the same as county, the sheriff's bailiwick extending over the county.
     2. In England, it signifies generally that liberty which is exempted
from the sheriff of the county over which the lord of the liberty appoints a
bailiff. Vide Wood's Inst. 206.