The character of being indefensible; indefensibility.(noun)
The Century Dictionary (Public Domain)
Use "indefensibleness" in a sentence
"The indefensibleness of the indiscriminate lesson giving consists in the fact that it is not the load but the harness that is too heavy."
"It was characteristic that, with all her debating, she was never troubled by the question whether the indefensibleness of her marriage did not include the fact that she had accepted Grandcourt solely as a man whom it was convenient for her to marry, not in the least as one to whom she would be binding herself in duty."
"As Redclyffe gave vent to this doctrine, which was not naturally his, but which had been the inculcation of a life, hitherto devoted to politics, he was surprised to find how strongly sensible he became of the ugliness and indefensibleness of what he said."