Choose the term that describes "toward the back of the body".

The term that refers to "toward the back of the body" is posterior. In anatomical terminology, reference points are essential for describing the locations of various structures in relation to one another. When something is positioned posteriorly, it means that it is located towards the back side of a person or organism.

In contrast, proximal relates to a position that is closer to the point of attachment or the trunk of the body, medial refers to being closer to the midline of the body, and rectilinear typically describes a type of motion along a straight line rather than a positional reference. Therefore, considering these definitions, posterior is the most accurate term to describe something located at the back of the body.