Wiktionary
undebatable
a. Not debatable; that cannot be debated.
Usage examples of "undebatable".
The case put forward by the colonists was historically strong, and there was much to be said for the contention that they were entitled to everything they claimed: on any view they could rightly complain of a cruel injustice, so long as the indolence or incompetence of English diplomacy suffered a debatable land to survive in the teeth of an undebatable argument.