Dubious (adjective)

1. Feeling or showing doubt about something.
2. Open to question or doubt.
3. Of uncertain outcome or quality.

Origin:

Dubious comes from the latin word "dubius" which means uncertain, and it was first recorded in the late 15th century.

Examples:

1. He had a dubious expression on his face when I told him the news.
2. She had a dubious expression on her face when I asked her to marry me.
3. The plan seems dubious at best.
4. I have a dubious feeling about this situation.
5. It was a dubious investment, but he decided to go through with it.