Learner's definition of QUESTIONABLE
1 : not likely to be true or correct : giving reason to doubt or question something
The truth of the statements was highly questionable.
a questionable conclusion
It is questionable whether this is the right decision. [=I question/doubt whether this is the right decision]
2 : likely to be bad : not worthy of trust
The water available in the village is of questionable quality.
a man of questionable character
They acquired the money through questionable means.
3 : not certain : unknown or undecided