The word "un-contestable" means something that cannot be challenged or disputed. Its antonyms are "questionable," "disputable," "contentious," "debatable," "contested," "doubted," "uncertain," and "ambiguous." A questionable claim or statement is one that is open to doubt or suspicion, while a disputable argument or decision is one that is not settled and can be argued against. Contentious issues or topics are highly controversial and often provoke heated disagreement. A debatable point or question is one that has plausible arguments on both sides. A contested result or outcome is one that is subject to dispute. Finally, an uncertain or ambiguous statement or decision is one that is not clear, certain, or definite.