Mr. Mowen glanced up dubiously: he could not tell whether the answer was intended to apply to him or to the young man.
They had been buying machinery from doubtful owners in sales of dubious legality, since nobody could tell who had the right to dispose of the great, dead properties, and nobody would come to challenge the transactions.
There are no more uses of "dubious" in the book.
Show samples from other sources
She was dubious, but agreed to come with us anyway.
She has a dubious reputation. I wouldn’t count on her.