This is the 11053rd most frequent Spanish word.
dudoso
Doubtful; uncertain; suspicious.
Here, 'dudoso' is used to indicate uncertainty about an event happening.
Es dudoso que venga a la fiesta.
It's doubtful that he will come to the party.
In this instance, 'dudosa' describes the questionable quality of an object.
Compré un producto de calidad dudosa.
I bought a product of dubious quality.
Here, 'dudosa' characterizes a person as having potentially questionable or untrustworthy motives.