indemonstrable

in·de·mon·stra·ble

I0098700 (ĭn′dĭ-mŏn′strə-bəl)adj. Impossible to prove or demonstrate: a seemingly valid but indemonstrable hypothesis.
in′de·mon′stra·bil′i·ty n.in′de·mon′stra·bly adv.

indemonstrable

(ˌɪndɪˈmɒnstrəbəl) adjincapable of being demonstrated or proved ˌindeˌmonstraˈbility n ˌindeˈmonstrably adv

in•de•mon•stra•ble

(ˌɪn dɪˈmɒn strə bəl, ɪnˈdɛm ən-)

adj. incapable of being demonstrated. [1560–70] in`de•mon′stra•bly, adv.
Translations
improuvableindémontrable