Antonyms of adj contestable

1 sense of contestable

Sense 1
contestable (vs. incontestable) -- (capable of being contested)

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")

Similarity of adj contestable

1 sense of contestable

Sense 1
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")
          Also See-> questionable#1