Source : Webster's Revised Unabridged Dictionary (1913)

Unhook \Un*hook"\, v. t. [1 st pref. un- + hook.]
   To loose from a hook; to undo or open by loosening or
   unfastening the hooks of; as, to unhook a fish; to unhook a
   dress.

Source : WordNet®

unhook
     v : take off a hook [ant: {hook}]