And it means exactly the same as unquestionable or undoubtable - so it's useless, as well.
Away with it!
Sunday Rest: indubitable. This word comes from the Latin indubitābilis, from dubitāre, to doubt (which is connected to our word double, and the idea of having to choose between two possibilities).
Hey, while I'm here, another annoying thing: the b in doubt was put in by scribes in the 1300s to make the word more like its Latin ancestors, which is a bit like insisting Prince Charles wears a codpiece...
...oh gosh, what a thought. I do hope he never does.