As an adjective questionable
is (obsolete) inviting questions; inviting inquiry.
As an adverb questionably is
in a questionable manner.
Other Comparisons: What's the difference?
(obsolete) Inviting questions; inviting inquiry.
* Shakespeare, Hamlet :
Problematic; open to doubt or challenge.
- Thou comest in such a questionable shape.
Of dubious respectability or morality.
- It is questionable if the universe is open or closed.
- Tiffiny's behavior is highly questionable .