dubious

Definitions

Hesitating or doubting; not to be relied upon.

Morally suspect or of questionable character.

Not clearly defined or of uncertain outcome.

Examples

The salesman made some dubious claims about the car's fuel efficiency.

I was rather dubious about his ability to finish the project on time.

Synonyms

doubtful uncertain skeptical questionable suspicious unreliable ambiguous

Antonyms

certain definite sure reliable trustworthy convinced undeniable