Yes, dubious is an adjective > (Of questionable character: dubious profits.)
credible
ambiguous, dubious, unclear, indecisive
unlikely , incredible , dubious , unbelievable .
Cautious IS an adjective. An adjective is an action!
Unsecured loans to high-risk creditors for dubious purposes.
Those letters spell the adjective dubious.
I was doubting that she was telling the truth^ In this answer doubting is used as a verb. The word doubting can be used as a verb (somehow informal because DOUBT is a stative verb). It can also be used as an adjective according to some dictionaries (although dubious would be the best word)It was a very doubting/dubious answer (an adjective)
unbelievable, incredible, beyond belief,inconceivable, unthinkable, unimaginable; unconvincing, far-fetched, dubious,implausible, improbable, unrealistic; hard to swallow.
present dubious tense
In Dubious Battle was created in 1936.
A Dubious Legacy was created in 1992.
"A Dubious Legacy" by Mary Wesley has approximately 352 pages.
John Steinbeck wrote In Dubious Battle.
In Dubious Battle has 270 pages.
He gave a dubious explanation for his absence from the meeting, raising suspicions among his colleagues.
The plan to separate the world into nations was quite dubious. Definition is here: http://www.merriam-webster.com/dictionary/dubious
A dubious disc is a hold item for Porygon2. If you trade a Porygon2 that's holding a dubious disc, it will evolve into Porygon-Z.