The Collaborative International Dictionary of English v.0.48:

Unbind \Un*bind"\ ([u^]n*b[imac]nd"), v. t. [imp. & p. p.
   Unbound ([u^]n*bound"); p. pr. & vb. n. Unbinding.] [AS.
   unbindan. See Un-, and Bind.]
   To remove a band from; to set free from shackles or
   fastenings; to untie; to unfasten; to loose; as, unbind your
   fillets; to unbind a prisoner's arms; to unbind a load.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unbind
    v 1: untie or unfasten; "unbind the feet of this poor woman"
         [ant: bind]