It means 'incontestable, non disputable, undoubted, non negotiable, (as we saw just before). Another word, deriving from this, is noun 'controversy'=αντιπαράθεση, διαμάχη. For ex. we have term ''incontroversble claims in court (those that can be proved), or 'incontrovertible legal arguments, or 'controversy in Court, between (for ex.) attorneys of plaintiff and defender, during course and process of interaction.