If you describe something as dubious, you mean that you do not consider it to be completely honest, safe, or reliable.
This claim seems to us to be rather dubious.
在我们看来,这项声明相当可疑。
If you are dubious about something, you are not completely sure about it and have not yet made up your mind about it.
My parents were a bit dubious about it all at first but we soon convinced them.
起初我父母亲对此尚心存疑虑,但很快我们便说服了他们。