unconscionable UK /ʌnˈkɒn.ʃən.ə.bəl/US /ˌənˈkɑn(t)ʃ(ə)nəbəl/ adjective2 •Not conscionable; unscrupulous and lacking principles or conscience. •Excessive, imprudent or unreasonable.The effective rate of interest was unconscionable, but not legally usurious. formsmore unconscionable · most unconscionable