Learn how to say Impugnable correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word impugn:
dispute the truth, validity, or honesty of (a statement or motive); call into question:
the father does not impugn her capacity as a good mother
late Middle English (also in the sense ‘assault, attack physically’): from Latin impugnare ‘assail’, from in- ‘towards’ + pugnare ‘fight’