The Collaborative International Dictionary of English v.0.48:

Unattached \Un`at*tached"\, a.
   1. Not attached; not adhering; having no engagement; free.
      [1913 Webster]

   2. (Mil.) Not assigned to any company or regiment.
      [1913 Webster]

   3. (Law) Not taken or arrested. --R. Junius.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unattached
    adj 1: not fastened together
    2: not associated in an exclusive sexual relationship [syn:
       unattached, uncommitted] [ant: attached, committed]
    3: (of animals) able to swim about; not attached [syn: free-
       swimming, unattached]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "unattached":
   afoot and lighthearted, apart, asunder, at large, at liberty,
   autonomous, bipartite, clear, detached, dichotomous, discontinuous,
   discrete, disengaged, distinct, divergent, easygoing, emancipated,
   footloose, footloose and fancy-free, free, free and easy,
   free as air, freeborn, freed, go-as-you-please, in the clear,
   in two, incoherent, independent, insular, liberated, loose,
   noncohesive, on the loose, partitioned, released, scot-free,
   self-governing, self-regulating, self-reliant, self-sustained,
   self-sustaining, separate, single, unaffiliated, unassociated,
   unattended, uncommitted, unconnected, unengaged, uninvolved,
   unjoined, unmarried