Definition of "unhook"

unhook

verb
third-person singular simple present unhooks, present participle unhooking, simple past and past participle unhooked
1. (transitive) To remove from a hook.
  Quotations
  A rather interesting and notable convenience, however, is that of ice water bags, which are hung on to the outside of the coaches at certain stops. These can be reached by leaning out of the window rather perilously, to unhook them, and paper cups are stocked in the compartments.
  1951 February, K. Westcott Jones, “Some Australian Railway Byways”, in Railway Magazine, page 118
  After Aulnoye the route lay through the colliery area and past Maubeuge to Jeumont, on the Belgian border. There Eùgene unhooked and we handed the train over to a Belgian diesel.
  1961 March, 'Balmore', “Driving and firing modern French steam locomotives”, in Trains Illustrated, page 146
2. (transitive) To unfasten by means of hooks.
  Quotations
  "She was standing in front of the mirror unhooking her frock. Mrs. P., I mean."
  1938, Norman Lindsay, Age of Consent, 1st Australian edition, Sydney, N.S.W.: Ure Smith, published 1962, page 82
3. (transitive, colloquial) To unfasten the bra of (its wearer).