The Collaborative International Dictionary of English v.0.48:

Unconscionable \Un*con"scion*a*ble\
   ([u^]n*k[o^]n"sh[u^]n*[.a]*b'l), a.
   1. Not conscionable; exceeding the limits of any reasonable
      claim or expectation; not conforming to reason;
      unreasonable; inordinate; extravagant; as, an
      unconscionable person or demand; unconscionable size.
      [1913 Webster]

            Which use of reason, most reasonless and
            unconscionable, is the utmost that any tyrant ever
            pretended.                            --Milton.
      [1913 Webster]

            His giantship is gone somewhat crestfallen,
            Stalking with less unconscionable strides. --Milton.
      [1913 Webster]

   2. Not guided by, or conformed to, conscience; that cannot be
      done in good conscience; as, unconscionable profits.
      [1913 Webster +PJC]

            Ungenerous as well as unconscionable practices.
                                                  --South.
      [1913 Webster] -- Un*con"scion*a*ble*ness, n. --
      Un*con"scion*a*bly, adv.
      [1913 Webster]