undeniable, incontestable or incontrovertible (adjective)
Examples of word unassailable
Her use of the expression unassailable patriarchy arguably may not include all male Catholics.
Here, in unassailable privacy, they do their tricks for one another, then bask in their own applause.
To be "unassailable" -- to exchange the soul of a Viking for that of a New Yorker, that of the quick pike for that of the lazy carp whose fat back grows moss covered in a dangerless pond -- that must never become the wish of a German.
Lord Justice Maurice Kay and Mr Justice Simon, sitting at the High Court in London, said it might be that Ms Smith's decision was "unassailable" - but ruled that Mr McKinnon had an arguable case that should be tested in court.
When Bernard Madoff made off with $50 billion from elite investors, it caused a virtual tectonic shift in the idea of unassailable integrity among the Wall Street chieftains.