WordNet sense 1 (subject to question):

questionable

WordNet sense 2 (of uncertain or ambiguous nature):

indeterminate

WordNet sense 3 (deliberately vague or ambiguous):

evasive

WordNet sense 4 (open to two or more interpretations; or of uncertain nature or significance; or (often) intended to mislead):

ambiguous

WordNet sense 5 (not conclusive; not putting an end to doubt or question):

inconclusive