Audacious is an adjective.
The meaning of audacious is 'daring or ready to take risks'. Although the meaning of audacious refers to daring but it emphasises on it and the word audacious is refers to a high degree of daredevil that is often considered foolish or silly.
There is another meaning of audacious which refers to 'daringly impolite and disrespectful'.
The following sentences make the meaning of audacious more clear.
1. I know you are an audacious person.
2. He is just trying to show his style doing stunts while many call him an audacious person for this.
3. He doesn't even respect his parents, really an audacious guy !