The Collaborative International Dictionary of English v.0.48:

Peaceable \Peace"a*ble\, a. [OE. peisible, F. paisible.]
   Begin in or at peace; tranquil; quiet; free from, or not
   disposed to, war, disorder, or excitement; not quarrelsome.
   -- Peace"a*ble*ness, n. -- Peace"a*bly, adv.
   [1913 Webster]

   Syn: Peaceful; pacific; tranquil; quiet; mild; undisturbed;
        serene; still.

   Usage: Peaceable, Peaceful. Peaceable describes the state
          of an individual, nation, etc., in reference to
          external hostility, attack, etc.; peaceful, in respect
          to internal disturbance. The former denotes "in the
          spirit of peace;" latter; "in the possession or
          enjoyment of peace." A peaceable adjustment of
          difficulties; a peaceful life, scene.
          [1913 Webster]

WordNet (r) 3.0 (2006):

peaceable
    adj 1: inclined or disposed to peace; "they met in a peaceable
           spirit"; "peace-loving citizens" [syn: peaceable,
           peace-loving]
    2: not disturbed by strife or turmoil or war; "a peaceful
       nation"; "peaceful times"; "a far from peaceful Christmas";
       "peaceful sleep" [syn: peaceful, peaceable] [ant:
       unpeaceful]
    3: disposed to peace or of a peaceful nature; "the pacific
       temper seeks to settle disputes on grounds of justice rather
       than by force"; "a quiet and peaceable person"; "in a
       peaceable and orderly manner" [syn: pacific, peaceable]

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "peaceable":
   agreeable, amiable, amicable, at peace, at rest, bland, bloodless,
   broken, brotherly, calm, chastened, civil, civilian, cloistered,
   compatible, complaisant, conciliatory, concordant, congenial, cool,
   cordial, domesticated, dovelike, dovish, dwindling, ebbing,
   even-tenored, favorable, fraternal, friendlike, friendly, genial,
   gentle, halcyon, harmonious, housebroken, humble, hushed, idyllic,
   impassive, inoffensive, irenic, isolated, judicious, kind,
   lamblike, meek, mild, mild as milk, moderate, moldering,
   neighborlike, neighborly, nonaggressive, noncombatant, nonmilitant,
   nonviolent, orderly, pacific, pacificatory, pacifist, pacifistic,
   pastoral, peace-loving, peaceful, peacetime, piping, placid,
   pleasant, prudent, quiescent, quiet, reposeful, reposing, restful,
   resting, secluded, sequestered, sequestrated, serene, sheltered,
   simpatico, sisterly, smooth, sober, sociable, soft, still,
   still as death, stillish, stilly, stoic, stolid, subdued,
   subsiding, sympathique, tame, tamed, temperate, tranquil,
   unagitated, unbellicose, uncontentious, undisturbed, unhostile,
   unmilitant, unmilitary, unmoved, unperturbed, unruffled,
   unstirring, untroubled, waning, well-affected, well-disposed,
   well-intentioned, well-meaning, well-meant