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]WordNet (r) 3.0 (2006):
unhitch v 1: unfasten or release from or as if from a hitch [ant: catch, hitch]