What adjective describes someone who is lacking in politeness or good manners?

The adjective that describes someone who is lacking in politeness or good manners is "churlish." This term specifically refers to a person who displays a rude or surly demeanor, often being ill-mannered or socially graceless in their interactions with others. Churlish behavior is characterized by a disregard for social norms of courtesy, making it an apt descriptor for someone who shows a lack of politeness.

In contrast, the other options denote positive traits. "Considerate" refers to being mindful of others' feelings and needs, showcasing polite and kind behavior. "Respectful" indicates a display of respect and regard for others, which is the opposite of lacking in manners. "Amicable" describes a friendly and agreeable nature, further emphasizing a courteous demeanor. Therefore, "churlish" is distinct in its focus on rudeness and lack of civility, making it the correct choice for this context.