Which word best describes someone who ruins a dinner party by being rude?

The word 'boorish' is the correct answer as it describes someone who is rude, insensitive, or ill-mannered, especially in social settings like a dinner party. Being boorish implies a lack of social graces and consideration for others, leading to a negative impact on the event. Adept means skilled or proficient, not rude, so it does not fit the context of ruining a dinner party through rudeness. Languid means lacking in spirit or interest, which is different from being rude and disruptive. Brawny means physically strong, which is unrelated to the behavior of being rude and inconsiderate at a social gathering.