This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. Open to doubt or challenge; problematic.

adj. Not yet determined or specified.

adj. Of dubious morality or respectability: a questionable reputation.

adj. Problematic; open to doubt or challenge

adj. Of dubious respectability or morality

adj. Admitting of being questioned; inviting, or seeming to invite, inquiry.

adj. Liable to question; subject to be doubted or called in question; problematical; doubtful; suspicious.

Capable of being questioned or inquired of; inviting or seeming to invite inquiry or conversation.

Liable to question; suspicious; doubtful; uncertain; disputable: as, the deed is of questionable authority; his veracity is questionable.

adj. subject to question

adj. able to be refuted

"I. iv.43 (180,4) questionable shape] [By _questionable_ is meant provoking question."

problematical    suspicious    debatable    soi-disant    supposed    funny    apocryphal    alleged    so-called    self-styled   

unquestionable   

ambiguous    obscure   

problematical    suspicious    uncertain    debatable    doubtful    disputable    arguable    controvertible    controversial    equivocal   

unquestionable   

dubious    exceptional    personal    risky    controversial    erroneous    ambiguous    improper    legitimate    acceptable