The Collaborative International Dictionary of English v.0.48:

Garrison \Gar"ri*son\, v. t. [imp. & p. p. Garrisoned; p. pr.
   & vb. n. Garrisoning.] (Mil.)
   (a) To place troops in, as a fortification, for its defense;
       to furnish with soldiers; as, to garrison a fort or town.
   (b) To secure or defend by fortresses manned with troops; as,
       to garrison a conquered territory.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Garrison \Gar"ri*son\, n. [OE. garnisoun, F. garnison garrison,
   in OF. & OE. also, provision, munitions, from garnir to
   garnish. See Garnish.] (Mil.)
   (a) A body of troops stationed in a fort or fortified town.
   (b) A fortified place, in which troops are quartered for its
       security.
       [1913 Webster]

   In garrison, in the condition of a garrison; doing duty in
      a fort or as one of a garrison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

garrison
    n 1: a fortified military post where troops are stationed [syn:
         garrison, fort]
    2: United States abolitionist who published an anti-slavery
       journal (1805-1879) [syn: Garrison, William Lloyd
       Garrison]
    3: the troops who maintain and guard a fortified place
    v 1: station (troops) in a fort or garrison

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "garrison":
   KP, acropolis, advance guard, arm, armed guard, armor, armor-plate,
   army, army group, bank, bank guard, barricade, bastion, battalion,
   battery, battle, battle group, beachhead, blockade, blockhouse,
   bridgehead, brigade, bulwark, bunker, cadre, castellate, castle,
   citadel, coast guard, cohort, column, combat command, combat team,
   company, cordon, cordon sanitaire, corps, crenellate, detachment,
   detail, dig in, division, donjon, embattle, entrench, fasthold,
   fastness, fence, field army, field train, file, flying column,
   fort, fortify, fortress, garrison house, goalie, goalkeeper,
   goaltender, guard, guarder, guardsman, hold, inlying picket,
   jailer, keep, kitchen police, legion, man, man the garrison,
   maniple, martello, martello tower, mine, mote, motte, organization,
   outfit, outguard, outpost, palisade, peel, peel tower, phalanx,
   picket, pillbox, platoon, posse, post, rank, rath, rear guard,
   regiment, safehold, section, security guard, squad, squadron,
   strong point, stronghold, tactical unit, task force, tower,
   tower of strength, train, train guard, troop, unit, van, vanguard,
   wall, ward, warder, wing



Easton's 1897 Bible Dictionary:

Garrison
   (1.) Heb. matstsab, a station; a place where one stands (1 Sam.
   14:12); a military or fortified post (1 Sam. 13:23; 14:1, 4, 6,
   etc.).

     (2.) Heb. netsib, a prefect, superintendent; hence a military
   post (1 Sam. 10:5; 13:3, 4; 2 Sam. 8:6). This word has also been
   explained to denote a pillar set up to mark the Philistine
   conquest, or an officer appointed to collect taxes; but the idea
   of a military post seems to be the correct one.

     (3.) Heb. matstsebah, properly a monumental column; improperly
   rendered pl. "garrisons" in Ezek. 26:11; correctly in Revised
   Version "pillars," marg. "obelisks," probably an idolatrous
   image.


U.S. Gazetteer Places (2000):

Garrison, MT -- U.S. Census Designated Place in Montana
   Population (2000):    112
   Housing Units (2000): 63
   Land area (2000):     9.539573 sq. miles (24.707379 sq. km)
   Water area (2000):    0.003367 sq. miles (0.008720 sq. km)
   Total area (2000):    9.542940 sq. miles (24.716099 sq. km)
   FIPS code:            30175
   Located within:       Montana (MT), FIPS 30
   Location:             46.537526 N, 112.826435 W
   ZIP Codes (1990):     59731
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Garrison, MT
    Garrison


U.S. Gazetteer Places (2000):

Garrison, NE -- U.S. village in Nebraska
   Population (2000):    67
   Housing Units (2000): 31
   Land area (2000):     0.117074 sq. miles (0.303221 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.117074 sq. miles (0.303221 sq. km)
   FIPS code:            18300
   Located within:       Nebraska (NE), FIPS 31
   Location:             41.175518 N, 97.164883 W
   ZIP Codes (1990):     68632
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Garrison, NE
    Garrison


U.S. Gazetteer Places (2000):

Garrison, ND -- U.S. city in North Dakota
   Population (2000):    1318
   Housing Units (2000): 655
   Land area (2000):     1.399947 sq. miles (3.625845 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.399947 sq. miles (3.625845 sq. km)
   FIPS code:            29460
   Located within:       North Dakota (ND), FIPS 38
   Location:             47.652917 N, 101.416567 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Garrison, ND
    Garrison


U.S. Gazetteer Places (2000):

Garrison, IA -- U.S. city in Iowa
   Population (2000):    413
   Housing Units (2000): 177
   Land area (2000):     0.246812 sq. miles (0.639240 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.246812 sq. miles (0.639240 sq. km)
   FIPS code:            30000
   Located within:       Iowa (IA), FIPS 19
   Location:             42.143604 N, 92.143015 W
   ZIP Codes (1990):     52229
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Garrison, IA
    Garrison


U.S. Gazetteer Places (2000):

Garrison, TX -- U.S. city in Texas
   Population (2000):    844
   Housing Units (2000): 372
   Land area (2000):     1.160319 sq. miles (3.005212 sq. km)
   Water area (2000):    0.000102 sq. miles (0.000263 sq. km)
   Total area (2000):    1.160421 sq. miles (3.005475 sq. km)
   FIPS code:            29060
   Located within:       Texas (TX), FIPS 48
   Location:             31.824899 N, 94.491299 W
   ZIP Codes (1990):     75946
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Garrison, TX
    Garrison


U.S. Gazetteer Places (2000):

Garrison, MD -- U.S. Census Designated Place in Maryland
   Population (2000):    7969
   Housing Units (2000): 3696
   Land area (2000):     3.123265 sq. miles (8.089220 sq. km)
   Water area (2000):    0.013628 sq. miles (0.035297 sq. km)
   Total area (2000):    3.136893 sq. miles (8.124517 sq. km)
   FIPS code:            31625
   Located within:       Maryland (MD), FIPS 24
   Location:             39.401055 N, 76.751073 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Garrison, MD
    Garrison


U.S. Gazetteer Places (2000):

Garrison, MN -- U.S. city in Minnesota
   Population (2000):    213
   Housing Units (2000): 191
   Land area (2000):     1.070925 sq. miles (2.773683 sq. km)
   Water area (2000):    0.014204 sq. miles (0.036788 sq. km)
   Total area (2000):    1.085129 sq. miles (2.810471 sq. km)
   FIPS code:            23192
   Located within:       Minnesota (MN), FIPS 27
   Location:             46.295851 N, 93.824368 W
   ZIP Codes (1990):     56450
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Garrison, MN
    Garrison