Definition of "unconscionable"

unconscionable

/ənˈkɔn.ʃən.ə.bəl/

adjective
comparative more unconscionable, superlative most unconscionable
1. Not conscionable; unscrupulous and lacking principles or conscience.
  Quotations
  When Roger assured him that prospects "looked very good" for a retrial, even a reversal of the verdict, since Roger had discovered "unconscionable errors" in the trial, Jackson grunted in bemusement and smiled with half his mouth.
  2001, Joyce Carol Oates, Middle Age: A Romance, paperback edition, Fourth Estate, page 364
2. Excessive, imprudent or unreasonable.
  Quotations
  [...] and the agrieved person shall doe more manly, to be extraordinary and singular in claiming the due right whereof he is frustrated, then to piece up his lost contentment by visiting the Stews, or stepping to his neighbours bed, which is the common shift in this mis-fortune, or els by suffering his usefull life to wast away and be lost under a secret affliction of an unconscionable size to humane strength.
  1643, John Milton, Doctrine and Discipline of Divorce
  He amazed the pretty hostess by refusing breakfast; however, flinging down double the amount of her already unconscionable bill, consoled her for his want of appetite.
  1837, L[etitia] E[lizabeth] L[andon], “The Past”, in Ethel Churchill: Or, The Two Brides. […], volume II, London: Henry Colburn, […], page 84