1. doubtful or uncertain; open to question or debate
2. of poor quality or reliability; not trustworthy
3. morally or ethically suspect; improper

Examples

• The witness gave questionable testimony that contradicted earlier statements.
• It’s questionable whether we’ll finish the project on time.
• The company’s questionable business practices led to an investigation.
• His questionable decision to skip the meeting upset his boss.
• The restaurant’s questionable hygiene standards worried health inspectors.
• She made some questionable choices during her teenage years.
• The study’s methodology is questionable and needs review.