Which word best describes something that is exactly opposite?

The term "antipodal" is derived from the Greek word "antipodes," which refers to points on the earth that are diametrically opposite to each other. In a broader sense, "antipodal" describes anything that is situated on the opposite side or is completely contrary in nature or position. This makes it a perfect fit for describing something that is exactly opposite.

In contrast, "bellicose" pertains to a nature inclined toward aggression or conflict. "Artless" refers to being free of deceit or craftiness, often implying a sense of simplicity or innocence rather than oppositeness. "Ascetic" is associated with practices of severe self-discipline and abstention from indulgence, which does not relate to the concept of oppositeness either.

Therefore, "antipodal" accurately captures the essence of being exactly opposite, positioning it as the correct choice among the options provided.