What term refers to a drawing showing the outline of an object?

The term that refers to a drawing showing the outline of an object is "silhouette." A silhouette typically depicts a solid shape filled with a single color, often black, against a lighter background, and it captures only the outline and basic form of the object without detailing any inner features. This artistic representation emphasizes the contour of the subject, making it instantly recognizable while omitting intricate details.

The other terms do not fit this definition as precisely. A portrait, for instance, generally focuses on depicting the likeness of a person, including detailed facial features and expressions, rather than just an outline. A diagram typically conveys information or instructions with labels and often includes various elements and annotations, moving beyond mere outlines to include specifics. A sketch is a rough or unfinished drawing that may include varying levels of detail but does not specifically refer to an outline alone. Thus, when it comes to representing the outline of an object succinctly, a silhouette stands out as the most accurate term.