unhitch

un- +‎ hitch

unhitch (third-person singular simple present unhitches, present participle unhitching, simple past and past participle unhitched)

1. To disconnect; to detach; to undo that which is hitched.
   • 1877, Anna Sewell, Black Beauty Chapter 23

     There is no knowing what further mischief she might have done, had not York promptly sat himself down flat on her head, to prevent her struggling, at the same time calling out, "Unbuckle the black horse! run for the winch and unscrew the carriage pole; cut the trace here—somebody, if you can't unhitch it."

• Hutchin