The Collaborative International Dictionary of English v.0.48:

Outpost \Out"post`\, n. (Mil.)
   (a) A post or station without the limits of a camp, or at a
       distance from the main body of an army, for observation
       of the enemy.
   (b) The troops placed at such a station.
       [1913 Webster]

WordNet (r) 3.0 (2006):

outpost
    n 1: a station in a remote or sparsely populated location [syn:
         outstation, outpost]
    2: a settlement on the frontier of civilization [syn: frontier
       settlement, outpost]
    3: a military post stationed at a distance from the main body of
       troops

Moby Thesaurus II by Grady Ward, 1.0:

135 Moby Thesaurus words for "outpost":
   Berlin wall, China, Darkest Africa, God knows where, Greenland,
   North Pole, Outer Mongolia, Pago Pago, Pillars of Hercules,
   Siberia, South Pole, Thule, Tierra del Fuego, Timbuktu,
   Ultima Thule, Yukon, advance guard, airhead, alentours, ambience,
   ambit, antipodes, armed guard, avant-garde, back country,
   backwoods, bamboo curtain, bank guard, battle line, beachhead,
   boondock, boondocks, border, border ground, borderland,
   borderlands, bridgehead, brush, bush country, bushveld, circle,
   circuit, circumambiencies, circumjacencies, circumstances,
   coast guard, compass, context, cordon, cordon sanitaire, entourage,
   environing circumstances, environment, environs, farthest outpost,
   first line, forefront, forests, front, front line, front rank,
   front-runner, frontier, frontier post, garrison, gestalt, goalie,
   goalkeeper, goaltender, godforsaken place, guard, guarder,
   guardsman, habitat, hinterland, inlying picket, iron curtain,
   jailer, jumping-off place, line, march, marches, marchland, milieu,
   neighborhood, nowhere, outback, outer space, outguard, outposts,
   outskirts, perimeter, periphery, picket, pioneer, point, pole,
   precincts, precursor, purlieus, railhead, rear guard, scout,
   security guard, situation, spearhead, suburbs, surroundings,
   the Great Divide, the South Seas, the boondocks, the bush,
   the moon, the sticks, the tullies, three-mile limit, timbers,
   total environment, train guard, twelve-mile limit,
   uninhabited region, up-country, van, vanguard, vicinage, vicinity,
   virgin land, virgin territory, warder, wasteland, wild West,
   wilderness, wilds, woodlands, woods