The Collaborative International Dictionary
Challengeable
Challengeable \Chal"lenge*a*ble\, a. That may be challenged.
Wiktionary
challengeable
a. Able to be challenged or disputed.
WordNet
challengeable
adj. capable of being challenged
Usage examples of "challengeable".
It was not that he told deliberate lies -he might have seemed more human and fallible if he did he merely made huge assumptions which then became Holy Writ, part of the un challengeable Gospel according to Dunster.