The Collaborative International Dictionary of English v.0.48:

Warren \War"ren\ (w[o^]r"r[e^]n), n. [OF. waresne, warenne,
   garene, F. garenne, from OF. warer, garer, to beware, to take
   care; of Teutonic origin; cf. OHG. war[=o]n (in comp.), OS.
   war[=o]n to take care, to observe, akin to E. wary.
   [root]142. See Wary.]
   [1913 Webster]
   1. (Eng Law)
      (a) A place privileged, by prescription or grant the king,
          for keeping certain animals (as hares, conies,
          partridges, pheasants, etc.) called beasts and fowls
          of warren. --Burrill.
      (b) A privilege which one has in his lands, by royal grant
          or prescription, of hunting and taking wild beasts and
          birds of warren, to the exclusion of any other person
          not entering by his permission. --Spelman.
          [1913 Webster]

                They wend both warren and in waste. --Piers
                                                  Plowman.
          [1913 Webster]

   Note: The warren is the next franchise in degree to the park;
         and a forest, which is the highest in dignity,
         comprehends a chase, a park, and a free warren.
         [1913 Webster]

   2. A piece of ground for the breeding of rabbits.
      [1913 Webster]

   3. A place for keeping flash, in a river.
      [1913 Webster]

U.S. Gazetteer (1990):

Warren, AR (city, FIPS 73310)
  Location: 33.61014 N, 92.06967 W
  Population (1990): 6455 (2819 housing units)
  Area: 16.9 sq km (land), 0.1 sq km (water)
  Zip code(s): 71671
Warren, CT
  Zip code(s): 06754
Warren, IL (village, FIPS 78851)
  Location: 42.49473 N, 89.99018 W
  Population (1990): 1550 (673 housing units)
  Area: 2.4 sq km (land), 0.0 sq km (water)
  Zip code(s): 61087
Warren, IN (town, FIPS 80108)
  Location: 40.68667 N, 85.42337 W
  Population (1990): 1185 (521 housing units)
  Area: 2.0 sq km (land), 0.0 sq km (water)
  Zip code(s): 46792
Warren, MA (CDP, FIPS 73055)
  Location: 42.21522 N, 72.19067 W
  Population (1990): 1516 (637 housing units)
  Area: 3.3 sq km (land), 0.0 sq km (water)
Warren, ME
  Zip code(s): 04864
Warren, MI (city, FIPS 84000)
  Location: 42.49300 N, 83.02820 W
  Population (1990): 144864 (56189 housing units)
  Area: 88.8 sq km (land), 0.1 sq km (water)
  Zip code(s): 48089, 48091, 48092, 48093
Warren, MN (city, FIPS 68170)
  Location: 48.19606 N, 96.76984 W
  Population (1990): 1813 (830 housing units)
  Area: 3.1 sq km (land), 0.0 sq km (water)
Warren, NH
  Zip code(s): 03279
Warren, NJ
  Zip code(s): 07059
Warren, OH (city, FIPS 80892)
  Location: 41.23805 N, 80.81690 W
  Population (1990): 50793 (21785 housing units)
  Area: 41.4 sq km (land), 0.1 sq km (water)
  Zip code(s): 44481, 44483, 44484, 44485
Warren, OR
  Zip code(s): 97053
Warren, PA (city, FIPS 81000)
  Location: 41.84373 N, 79.14405 W
  Population (1990): 11122 (5223 housing units)
  Area: 7.6 sq km (land), 0.5 sq km (water)
Warren, RI
  Zip code(s): 02885
Warren, TX
  Zip code(s): 77664

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "warren":
   Augean stables, Hydra, abri, antre, bunker, burrow, cave, cavern,
   cove, dugout, dump, foxhole, grot, grotto, hole, hotbed, hovel,
   lair, milk cow, mustard, pesthole, pigpen, pigsty, plague spot,
   rabbit, rich soil, rookery, seed plot, sewer, slum, stable, sty,
   subterrane, subway, tenement, the slums, tunnel