1. feeling doubt or uncertainty about something
2. questionable or suspicious in quality, authenticity, or reliability

Examples

• She was dubious about his claims of having climbed Mount Everest.
• The witness gave a dubious account of what happened that night.
• I’m dubious that we can finish this project by tomorrow.
• The painting’s authenticity is dubious according to art experts.
• He made some dubious business deals that landed him in trouble.
• The restaurant had dubious hygiene standards.
• Her dubious expression showed she didn’t believe the story.