unhitch

from WordNet (r) 3.0 (2006)

unhitch
    v 1: unfasten or release from or as if from a hitch [ant:
         {catch}, {hitch}]

from The Collaborative International Dictionary of English v.0.48

unhitch \un*hitch"\, v. t. [1st pref. un- + hitch.]
   To free from being hitched, or as if from being hitched; to
   unfasten; to loose; as, to unhitch a horse, or a trace.
   [1913 Webster]