The Collaborative International Dictionary of English v.0.48:

Unmanned \Un*manned"\, a.
   1. [Properly p. p. of unman.] Deprived of manly qualities;
      deficient in vigor, strength, courage, etc.; weak;
      effeminate.
      [1913 Webster]

   2. [Pref. un- not + man + -ed.] (Falconry) Not tamed; not
      made familiar with, or subject to, man; -- also used
      figuratively. [Obs.]
      [1913 Webster]

            Hood my unmanned blood bating in my cheeks
            With thy black mantle.                --Shak.
      [1913 Webster]

   3. [Pref. un- not + manned.] Not furnished with men; as, an
      unmanned ship.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unmanned
    adj 1: lacking a crew; "an unmanned satellite to Mars" [syn:
           unmanned, remote-controlled] [ant: manned]

Moby Thesaurus II by Grady Ward, 1.0:

117 Moby Thesaurus words for "unmanned":
   abandoned, afraid, aghast, appalled, ashen, astounded, available,
   awed, awestricken, awestruck, blanched, castrated, chicken,
   chickenhearted, coward, cowardly, cowed, crushed, dashed, daunted,
   deadly pale, debilitated, demasculinized, demoralized, deserted,
   devitalized, dismayed, effeminized, emasculate, emasculated,
   enervated, eunuchized, fainthearted, fearful, forsaken, free,
   frozen, funking, funky, gelded, godforsaken, gray with fear,
   henhearted, horrified, horror-struck, intimidated, lily-livered,
   lustless, marrowless, milk-livered, milksoppish, milksoppy, mousy,
   nerveless, neurasthenic, open, overcome, overtimid, overtimorous,
   pale as death, pallid, panic-prone, panicky, paralyzed, petrified,
   pigeonhearted, pithless, prostrate, prostrated, rabbity,
   reduced to jelly, scared stiff, scared to death, shaken, shot,
   shot to pieces, sinewless, sissified, sissy, soft, stricken,
   stunned, stupefied, tenantless, terrified, terror-crazed,
   terror-haunted, terror-ridden, terror-riven, terror-shaken,
   terror-smitten, terror-struck, terror-troubled, timid, timorous,
   undone, unfilled, unglued, uninhabited, unmanly, unnerved,
   unoccupied, unpeopled, unpopulated, unsexed, unstaffed, unstrung,
   untaken, untenanted, untended, upset, vacant, weak, weak-kneed,
   weakhearted, white-livered, yellow