Antonyms of adj incontestable

2 senses of incontestable

Sense 1
incontestable (vs. contestable), incontestible -- (incapable of being contested or disputed)

contestable (vs. incontestable) -- (capable of being contested)
        => challengeable -- (capable of being challenged)
        => debatable, disputable -- (capable of being disproved)
        => shakable, shakeable -- (capable of being weakened; "the crisis proved his confidence was shakable")

Sense 2
incontestable, indisputable, undisputable -- (not open to question; obviously true; "undeniable guilt"; "indisputable evidence of a witness")

INDIRECT (VIA undeniable) -> deniable -- (capable of being denied or contradicted)

Similarity of adj incontestable

2 senses of incontestable

Sense 1
incontestable (vs. contestable), incontestible -- (incapable of being contested or disputed)
       => demonstrable, incontrovertible -- (necessarily or demonstrably true; "demonstrable truths")
       => demonstrated -- (having been demonstrated or verified beyond doubt)
       => inarguable, unarguable -- (against which no argument can be made)
       => unassailable, unshakable, watertight, bulletproof -- (without flaws or loopholes; "an ironclad contract"; "a watertight alibi"; "a bulletproof argument")
       => unanswerable -- (impossible to answer; "an unanswerable argument")
          Also See-> unquestionable#1

Sense 2
incontestable, indisputable, undisputable -- (not open to question; obviously true; "undeniable guilt"; "indisputable evidence of a witness")
       => undeniable (vs. deniable) -- (not possible to deny)