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]