Step 1: Understand the meaning of the sentence.
The phrase without manners or polish describes a person who is rude, ill-mannered, and lacking refinement in behavior. We need the word that best expresses this quality.
Step 2: Analyze the options.
Rustic refers to someone from the countryside or something simple and rural. It does not necessarily mean ill-mannered.
Naive means innocent, inexperienced, or lacking worldly knowledge. This is not related to bad manners.
Boorish means rude, coarse, and ill-mannered. It is the exact word for a person who lacks manners or polish.
Barbarian usually refers to an uncivilized or cruel person, often in a stronger historical or figurative sense. It is not the most precise answer here.
Step 3: Conclusion.
Thus, a person without manners or polish is called boorish.