The Collaborative International Dictionary of English v.0.48:

Dispassionate \Dis*pas"sion*ate\, a.
   1. Free from passion; not warped, prejudiced, swerved, or
      carried away by passion or feeling; judicial; calm;
      composed.
      [1913 Webster]

            Wise and dispassionate men.           --Clarendon.
      [1913 Webster]

   2. Not dictated by passion; not proceeding from temper or
      bias; impartial; as, dispassionate proceedings; a
      dispassionate view.

   Syn: Calm; cool; composed serene; unimpassioned; temperate;
        moderate; impartial; unruffled. --
        Dis*pas"sion*ate*ly, adv. -- Dis*pas"sion*ate*ness,
        n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

dispassionate
    adj 1: unaffected by strong emotion or prejudice; "a journalist
           should be a dispassionate reporter of fact" [syn:
           dispassionate, cold-eyed]

Moby Thesaurus II by Grady Ward, 1.0:

139 Moby Thesaurus words for "dispassionate":
   Olympian, aboveboard, abstract, affectless, aloof, anesthetized,
   apathetic, arctic, ataractic, autistic, blase, blunt, bovine, calm,
   candid, careless, casual, catatonic, chill, chilly, cold,
   cold as charity, cold-blooded, coldhearted, colorless, composed,
   cool, detached, devil-may-care, disinterested, disregardful,
   drugged, dull, easygoing, emotionally dead, emotionless, equable,
   equal, equitable, even, even-tempered, evenhanded, fair, frank,
   frigid, frosted, frosty, frozen, heartless, heedless, icy,
   immovable, impartial, impassible, impassive, impersonal,
   imperturbable, inattentive, incurious, indifferent, inexcitable,
   inirritable, insouciant, insusceptible, just, lackadaisical,
   level-headed, levelheaded, listless, lofty, mindless, negligent,
   neutral, nonchalant, nonemotional, objective, obtuse, open,
   open-minded, out of touch, passionless, patient, peaceful,
   perfunctory, placid, pococurante, poker-faced, reckless,
   regardless, reposeful, self-absorbed, self-controlled,
   self-possessed, selfless, serene, sober, soulless, spiritless,
   steady, stoic, stolid, straightforward, tranquil, turned-off,
   unaffectionate, unanxious, unbiased, uncolored, unconcerned,
   undazzled, undiscriminating, undisturbable, unemotional,
   unexcitable, unexcited, unfeeling, unflappable, unimpassioned,
   unimpressionable, uninfluenced, uninterested, unirritable,
   unjaundiced, unloving, unmindful, unmoved, unnervous, unpassionate,
   unprejudiced, unprepossessed, unresponding, unresponsive,
   unruffled, unselfish, unsolicitous, unsusceptible, unswayed,
   unsympathetic, untouchable